diff --git a/AK/Assertions.cpp b/AK/Assertions.cpp
index 9334a49ad5725..c4e09b41415aa 100644
--- a/AK/Assertions.cpp
+++ b/AK/Assertions.cpp
@@ -23,11 +23,7 @@
 #    include <cxxabi.h>
 #endif
 
-#if defined(AK_OS_SERENITY)
-#    define ERRORLN dbgln
-#else
-#    define ERRORLN warnln
-#endif
+#define ERRORLN warnln
 
 #if defined(AK_HAS_BACKTRACE_HEADER)
 namespace {
@@ -83,7 +79,7 @@ extern "C" {
 
 void ak_verification_failed(char const* message)
 {
-#if defined(AK_OS_SERENITY) || defined(AK_OS_ANDROID)
+#if defined(AK_OS_ANDROID)
     bool colorize_output = true;
 #elif defined(AK_OS_WINDOWS)
     bool colorize_output = false;
diff --git a/AK/BumpAllocator.h b/AK/BumpAllocator.h
index 21348a4df0c0d..db0c629f6c232 100644
--- a/AK/BumpAllocator.h
+++ b/AK/BumpAllocator.h
@@ -103,11 +103,7 @@ class BumpAllocator {
         void* new_chunk = reinterpret_cast<void*>(s_unused_allocation_cache.exchange(0));
         if (!new_chunk) {
             if constexpr (use_mmap) {
-#ifdef AK_OS_SERENITY
-                new_chunk = serenity_mmap(nullptr, m_chunk_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_RANDOMIZED | MAP_PRIVATE, 0, 0, m_chunk_size, "BumpAllocator Chunk");
-#else
                 new_chunk = mmap(nullptr, m_chunk_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-#endif
                 if (new_chunk == MAP_FAILED)
                     return false;
             } else {
diff --git a/AK/Error.h b/AK/Error.h
index f8b60690ad876..3d241a9392e95 100644
--- a/AK/Error.h
+++ b/AK/Error.h
@@ -154,13 +154,6 @@ class [[nodiscard]] ErrorOr {
     {
     }
 
-#ifdef AK_OS_SERENITY
-    ErrorOr(ErrnoCode code)
-        : m_value_or_error(Error::from_errno(code))
-    {
-    }
-#endif
-
     T& value()
     {
         return m_value_or_error.template get<T>();
diff --git a/AK/Format.cpp b/AK/Format.cpp
index f8083a5ff592d..672323b9ba148 100644
--- a/AK/Format.cpp
+++ b/AK/Format.cpp
@@ -17,10 +17,6 @@
 #include <string.h>
 #include <time.h>
 
-#if defined(AK_OS_SERENITY)
-#    include <serenity.h>
-#endif
-
 #if defined(AK_OS_ANDROID)
 #    include <android/log.h>
 #endif
@@ -1114,13 +1110,7 @@ void vout(LogLevel log_level, StringView fmtstr, TypeErasedFormatParams& params,
 // FIXME: Deduplicate with Core::Process:get_name()
 [[gnu::used]] static ByteString process_name_helper()
 {
-#if defined(AK_OS_SERENITY)
-    char buffer[BUFSIZ] = {};
-    int rc = get_process_name(buffer, BUFSIZ);
-    if (rc != 0)
-        return ByteString {};
-    return StringView { buffer, strlen(buffer) };
-#elif defined(AK_LIBC_GLIBC) || (defined(AK_OS_LINUX) && !defined(AK_OS_ANDROID))
+#if defined(AK_LIBC_GLIBC) || (defined(AK_OS_LINUX) && !defined(AK_OS_ANDROID))
     return StringView { program_invocation_name, strlen(program_invocation_name) };
 #elif defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
     auto const* progname = getprogname();
@@ -1154,13 +1144,7 @@ void set_debug_enabled(bool value)
     is_debug_enabled = value;
 }
 
-// On Serenity, dbgln goes to a non-stderr output
-static bool is_rich_debug_enabled =
-#if defined(AK_OS_SERENITY)
-    true;
-#else
-    false;
-#endif
+static bool is_rich_debug_enabled = false;
 
 void set_rich_debug_enabled(bool value)
 {
@@ -1181,7 +1165,7 @@ void vdbg(StringView fmtstr, TypeErasedFormatParams& params, bool newline)
             struct timespec ts = {};
             clock_gettime(CLOCK_MONOTONIC_COARSE, &ts);
             auto pid = getpid();
-#    if defined(AK_OS_SERENITY) || defined(AK_OS_LINUX)
+#    if defined(AK_OS_LINUX)
             // Linux and Serenity handle thread IDs as if they are related to process ids
             auto tid = gettid();
             if (pid == tid)
@@ -1189,7 +1173,7 @@ void vdbg(StringView fmtstr, TypeErasedFormatParams& params, bool newline)
             {
                 builder.appendff("{}.{:03} \033[33;1m{}({})\033[0m: ", ts.tv_sec, ts.tv_nsec / 1000000, process_name, pid);
             }
-#    if defined(AK_OS_SERENITY) || defined(AK_OS_LINUX)
+#    if defined(AK_OS_LINUX)
             else {
                 builder.appendff("{}.{:03} \033[33;1m{}({}:{})\033[0m: ", ts.tv_sec, ts.tv_nsec / 1000000, process_name, pid, tid);
             }
diff --git a/AK/Math.h b/AK/Math.h
index 1a354a7488e91..c40060a113ecf 100644
--- a/AK/Math.h
+++ b/AK/Math.h
@@ -420,10 +420,6 @@ constexpr T fmod(T x, T y)
     //        might work
 
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     if constexpr (IsSame<T, long double>)
         return __builtin_fmodl(x, y);
     if constexpr (IsSame<T, double>)
@@ -449,10 +445,6 @@ constexpr T remainder(T x, T y)
     } while (fpu_status & 0x400);
     return x;
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     if constexpr (IsSame<T, long double>)
         return __builtin_remainderl(x, y);
     if constexpr (IsSame<T, double>)
@@ -559,13 +551,7 @@ constexpr T sin(T angle)
         : "0"(angle));
     return ret;
 #else
-#    if defined(AK_OS_SERENITY)
-    // FIXME: This is a very naive implementation, and is only valid for small x.
-    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
-    return angle;
-#    else
     return __builtin_sin(angle);
-#    endif
 #endif
 }
 
@@ -582,13 +568,7 @@ constexpr T cos(T angle)
         : "0"(angle));
     return ret;
 #else
-#    if defined(AK_OS_SERENITY)
-    // FIXME: This is a very naive implementation, and is only valid for small x.
-    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
-    return 1 - ((angle * angle) / 2);
-#    else
     return __builtin_cos(angle);
-#    endif
 #endif
 }
 
@@ -625,13 +605,7 @@ constexpr T tan(T angle)
 
     return ret;
 #else
-#    if defined(AK_OS_SERENITY)
-    // FIXME: This is a very naive implementation, and is only valid for small x.
-    //        Probably a good idea to use a better algorithm in the future, such as a taylor approximation.
-    return angle;
-#    else
     return __builtin_tan(angle);
-#    endif
 #endif
 }
 
@@ -649,10 +623,6 @@ constexpr T atan(T value)
         : "0"(value));
     return ret;
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     return __builtin_atan(value);
 #endif
 }
@@ -708,10 +678,6 @@ constexpr T atan2(T y, T x)
         : "st(1)");
     return ret;
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     return __builtin_atan2(y, x);
 #endif
 }
@@ -826,9 +792,6 @@ constexpr T log(T x)
         : "=t"(ret)
         : "0"(x));
     return ret;
-#elif defined(AK_OS_SERENITY)
-    // FIXME: Adjust the polynomial and formula in log2 to fit this
-    return log2<T>(x) / L2_E<T>;
 #else
     return __builtin_log(x);
 #endif
@@ -848,9 +811,6 @@ constexpr T log10(T x)
         : "=t"(ret)
         : "0"(x));
     return ret;
-#elif defined(AK_OS_SERENITY)
-    // FIXME: Adjust the polynomial and formula in log2 to fit this
-    return log2<T>(x) / L2_10<T>;
 #else
     return __builtin_log10(x);
 #endif
@@ -876,10 +836,6 @@ constexpr T exp(T exponent)
         : "0"(exponent));
     return res;
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     return __builtin_exp(exponent);
 #endif
 }
@@ -902,10 +858,6 @@ constexpr T exp2(T exponent)
         : "0"(exponent));
     return res;
 #else
-#    if defined(AK_OS_SERENITY)
-    // TODO: Add implementation for this function.
-    TODO();
-#    endif
     return __builtin_exp2(exponent);
 #endif
 }
diff --git a/AK/NoAllocationGuard.h b/AK/NoAllocationGuard.h
index 8cc3c846bad5e..c98af135c7223 100644
--- a/AK/NoAllocationGuard.h
+++ b/AK/NoAllocationGuard.h
@@ -9,10 +9,6 @@
 #include <AK/Forward.h>
 #include <AK/Noncopyable.h>
 
-#if defined(AK_OS_SERENITY)
-#    include <mallocdefs.h>
-#endif
-
 namespace AK {
 
 class NoAllocationGuard {
@@ -34,21 +30,12 @@ class NoAllocationGuard {
 private:
     static bool get_thread_allocation_state()
     {
-#if defined(AK_OS_SERENITY)
-        // This extern thread-local lives in our LibC, which doesn't exist on other systems.
-        return s_allocation_enabled;
-#else
         return true;
-#endif
     }
 
     static void set_thread_allocation_state(bool value)
     {
-#if defined(AK_OS_SERENITY)
-        s_allocation_enabled = value;
-#else
         (void)value;
-#endif
     }
 
     bool m_allocation_enabled_previously { true };
diff --git a/AK/Platform.h b/AK/Platform.h
index b75aa087e7649..6d951b7001d13 100644
--- a/AK/Platform.h
+++ b/AK/Platform.h
@@ -68,10 +68,6 @@
 #    define AK_LIBC_GLIBC_PREREQ(maj, min) 0
 #endif
 
-#if defined(__serenity__)
-#    define AK_OS_SERENITY
-#endif
-
 #if defined(__linux__)
 #    define AK_OS_LINUX
 #endif
@@ -248,15 +244,13 @@
 #    define LSAN_UNREGISTER_ROOT_REGION(base, size)
 #endif
 
-#ifndef AK_OS_SERENITY
-#    ifdef AK_OS_WINDOWS
+#ifdef AK_OS_WINDOWS
 // FIXME: No idea where to get this, but it's 4096 anyway :^)
-#        define PAGE_SIZE 4096
-#    else
-#        include <unistd.h>
-#        undef PAGE_SIZE
-#        define PAGE_SIZE sysconf(_SC_PAGESIZE)
-#    endif
+#    define PAGE_SIZE 4096
+#else
+#    include <unistd.h>
+#    undef PAGE_SIZE
+#    define PAGE_SIZE sysconf(_SC_PAGESIZE)
 #endif
 
 #if defined(AK_OS_WINDOWS)
diff --git a/AK/Random.h b/AK/Random.h
index c2badd3e6ac64..70eacd3021cd1 100644
--- a/AK/Random.h
+++ b/AK/Random.h
@@ -20,7 +20,7 @@ namespace AK {
 
 inline void fill_with_random([[maybe_unused]] Bytes bytes)
 {
-#if defined(AK_OS_SERENITY) || defined(AK_OS_ANDROID) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU) || AK_LIBC_GLIBC_PREREQ(2, 36)
+#if defined(AK_OS_ANDROID) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU) || AK_LIBC_GLIBC_PREREQ(2, 36)
     arc4random_buf(bytes.data(), bytes.size());
 #elif defined(OSS_FUZZ)
 #else
diff --git a/AK/Singleton.h b/AK/Singleton.h
index b1a0d5527f96a..c8b06dad1ea8a 100644
--- a/AK/Singleton.h
+++ b/AK/Singleton.h
@@ -19,9 +19,7 @@ extern "C" __declspec(dllimport) void __stdcall Sleep(unsigned long);
 #    include <sched.h>
 #endif
 
-#ifndef AK_OS_SERENITY
-#    include <new>
-#endif
+#include <new>
 
 namespace AK {
 
diff --git a/AK/StackInfo.cpp b/AK/StackInfo.cpp
index 4777c48375d1f..312e221b1c068 100644
--- a/AK/StackInfo.cpp
+++ b/AK/StackInfo.cpp
@@ -10,9 +10,7 @@
 #include <stdio.h>
 #include <string.h>
 
-#ifdef AK_OS_SERENITY
-#    include <serenity.h>
-#elif defined(AK_OS_LINUX) || defined(AK_LIBC_GLIBC) || defined(AK_OS_MACOS) || defined(AK_OS_IOS) || defined(AK_OS_NETBSD) || defined(AK_OS_SOLARIS) || defined(AK_OS_HAIKU)
+#if defined(AK_OS_LINUX) || defined(AK_LIBC_GLIBC) || defined(AK_OS_MACOS) || defined(AK_OS_IOS) || defined(AK_OS_NETBSD) || defined(AK_OS_SOLARIS) || defined(AK_OS_HAIKU)
 #    include <pthread.h>
 #    include <sys/resource.h>
 #elif defined(AK_OS_FREEBSD) || defined(AK_OS_OPENBSD)
@@ -28,12 +26,7 @@ namespace AK {
 
 StackInfo::StackInfo()
 {
-#ifdef AK_OS_SERENITY
-    if (get_stack_bounds(&m_base, &m_size) < 0) {
-        perror("get_stack_bounds");
-        VERIFY_NOT_REACHED();
-    }
-#elif defined(AK_OS_LINUX) or defined(AK_LIBC_GLIBC) or defined(AK_OS_FREEBSD) or defined(AK_OS_NETBSD) or defined(AK_OS_SOLARIS) or defined(AK_OS_HAIKU)
+#if defined(AK_OS_LINUX) or defined(AK_LIBC_GLIBC) or defined(AK_OS_FREEBSD) or defined(AK_OS_NETBSD) or defined(AK_OS_SOLARIS) or defined(AK_OS_HAIKU)
     int rc;
     pthread_attr_t attr;
     pthread_attr_init(&attr);
diff --git a/AK/Types.h b/AK/Types.h
index de00fccb4dda0..ae43413694190 100644
--- a/AK/Types.h
+++ b/AK/Types.h
@@ -110,41 +110,17 @@ using Conditional = typename __Conditional<condition, TrueType, FalseType>::Type
 
 }
 
-#ifdef AK_OS_SERENITY
+#include <stddef.h>
+#include <stdint.h>
+#include <sys/types.h>
 
-using size_t = __SIZE_TYPE__;
-using ssize_t = AK::Detail::MakeSigned<size_t>;
-
-using ptrdiff_t = __PTRDIFF_TYPE__;
-
-using intptr_t = __INTPTR_TYPE__;
-using uintptr_t = __UINTPTR_TYPE__;
-
-using uint8_t = u8;
-using uint16_t = u16;
-using uint32_t = u32;
-using uint64_t = u64;
-
-using int8_t = i8;
-using int16_t = i16;
-using int32_t = i32;
-using int64_t = i64;
-
-using pid_t = int;
-
-#else
-#    include <stddef.h>
-#    include <stdint.h>
-#    include <sys/types.h>
-
-#    ifdef __ptrdiff_t
+#ifdef __ptrdiff_t
 using __ptrdiff_t = __PTRDIFF_TYPE__;
-#    endif
+#endif
 
-#    if defined(AK_OS_WINDOWS)
+#if defined(AK_OS_WINDOWS)
 using ssize_t = AK::Detail::MakeSigned<size_t>;
 using mode_t = unsigned short;
-#    endif
 #endif
 
 using FlatPtr = AK::Detail::Conditional<sizeof(void*) == 8, u64, u32>;
diff --git a/AK/kmalloc.cpp b/AK/kmalloc.cpp
index a24444d7e2bea..b56ffe592c3b4 100644
--- a/AK/kmalloc.cpp
+++ b/AK/kmalloc.cpp
@@ -6,64 +6,3 @@
  */
 
 #include <AK/kmalloc.h>
-
-#if defined(AK_OS_SERENITY)
-
-#    include <AK/Assertions.h>
-
-// However deceptively simple these functions look, they must not be inlined.
-// Memory allocated in one translation unit has to be deallocatable in another
-// translation unit, so these functions must be the same everywhere.
-// By making these functions global, this invariant is enforced.
-
-void* operator new(size_t size)
-{
-    void* ptr = malloc(size);
-    VERIFY(ptr);
-    return ptr;
-}
-
-void* operator new(size_t size, std::nothrow_t const&) noexcept
-{
-    return malloc(size);
-}
-
-void operator delete(void* ptr) noexcept
-{
-    return free(ptr);
-}
-
-void operator delete(void* ptr, size_t) noexcept
-{
-    return free(ptr);
-}
-
-void* operator new[](size_t size)
-{
-    void* ptr = malloc(size);
-    VERIFY(ptr);
-    return ptr;
-}
-
-void* operator new[](size_t size, std::nothrow_t const&) noexcept
-{
-    return malloc(size);
-}
-
-void operator delete[](void* ptr) noexcept
-{
-    return free(ptr);
-}
-
-void operator delete[](void* ptr, size_t) noexcept
-{
-    return free(ptr);
-}
-
-// This is usually provided by libstdc++ in most cases, and the kernel has its own definition in
-// Kernel/Heap/kmalloc.cpp. If neither of those apply, the following should suffice to not fail during linking.
-namespace AK_REPLACED_STD_NAMESPACE {
-nothrow_t const nothrow;
-}
-
-#endif
diff --git a/AK/kmalloc.h b/AK/kmalloc.h
index 74822c50d19e0..d0276b94333ce 100644
--- a/AK/kmalloc.h
+++ b/AK/kmalloc.h
@@ -21,16 +21,14 @@ inline void kfree_sized(void* ptr, size_t)
     free(ptr);
 }
 
-#ifndef AK_OS_SERENITY
-#    include <AK/Types.h>
+#include <AK/Types.h>
 
-#    ifndef AK_OS_MACOS
+#ifndef AK_OS_MACOS
 extern "C" {
 inline size_t malloc_good_size(size_t size) { return size; }
 }
-#    else
-#        include <malloc/malloc.h>
-#    endif
+#else
+#    include <malloc/malloc.h>
 #endif
 
 using std::nothrow;
diff --git a/Tests/LibAudio/TestPlaybackStream.cpp b/Tests/LibAudio/TestPlaybackStream.cpp
index 8f14413a9a824..6988ea2db6459 100644
--- a/Tests/LibAudio/TestPlaybackStream.cpp
+++ b/Tests/LibAudio/TestPlaybackStream.cpp
@@ -21,18 +21,14 @@
 //        current session ID is 0, and AudioServer's socket address depends on the current sid.
 //        If we can fix that, this test can run on CI.
 //        https://github.com/SerenityOS/serenity/issues/20538
-#if defined(AK_OS_SERENITY)
-#    define STREAM_TEST BENCHMARK_CASE
-#else
-#    define STREAM_TEST TEST_CASE
-#endif
+#define STREAM_TEST TEST_CASE
 
 STREAM_TEST(create_and_destroy_playback_stream)
 {
     Core::EventLoop event_loop;
 
     bool has_implementation = false;
-#if defined(AK_OS_SERENITY) || defined(HAVE_PULSEAUDIO) || defined(AK_OS_MACOS)
+#if defined(HAVE_PULSEAUDIO) || defined(AK_OS_MACOS)
     has_implementation = true;
 #endif
 
diff --git a/Tests/LibAudio/TestWav.cpp b/Tests/LibAudio/TestWav.cpp
index e8d89f2ec30a5..14ce45e731f14 100644
--- a/Tests/LibAudio/TestWav.cpp
+++ b/Tests/LibAudio/TestWav.cpp
@@ -39,12 +39,7 @@ static void run_test(StringView file_name, int const num_samples, int const chan
     auto out_file = TRY_OR_FAIL(FileSystem::TempFile::create_temp_file());
     auto out_path = out_file->path();
 
-// This makes sure that the tests will run both on target and in Lagom.
-#ifdef AK_OS_SERENITY
-    ByteString in_path = ByteString::formatted("/usr/Tests/LibAudio/WAV/{}", file_name);
-#else
     ByteString in_path = ByteString::formatted("WAV/{}", file_name);
-#endif
 
     auto loader = TRY_OR_FAIL(Audio::Loader::create(in_path));
 
diff --git a/Tests/LibCompress/TestBrotli.cpp b/Tests/LibCompress/TestBrotli.cpp
index 810d27cb2345b..3cd7839568cf9 100644
--- a/Tests/LibCompress/TestBrotli.cpp
+++ b/Tests/LibCompress/TestBrotli.cpp
@@ -68,12 +68,7 @@ TEST_CASE(dictionary_use_after_uncompressed_block)
 
 static void run_test(StringView const file_name)
 {
-    // This makes sure that the tests will run both on target and in Lagom.
-#ifdef AK_OS_SERENITY
-    ByteString path = ByteString::formatted("/usr/Tests/LibCompress/brotli-test-files/{}", file_name);
-#else
     ByteString path = ByteString::formatted("brotli-test-files/{}", file_name);
-#endif
 
     auto cmp_file = MUST(Core::File::open(path, Core::File::OpenMode::Read));
     auto cmp_data = MUST(cmp_file->read_until_eof());
@@ -139,12 +134,7 @@ TEST_CASE(brotli_single_x)
 
 TEST_CASE(brotli_decompress_zero_one_bin)
 {
-    // This makes sure that the tests will run both on target and in Lagom.
-#ifdef AK_OS_SERENITY
-    ByteString path = "/usr/Tests/LibCompress/brotli-test-files/zero-one.bin";
-#else
     ByteString path = "brotli-test-files/zero-one.bin";
-#endif
 
     ByteString path_compressed = ByteString::formatted("{}.br", path);
 
diff --git a/Tests/LibCompress/TestDeflate.cpp b/Tests/LibCompress/TestDeflate.cpp
index eb9899f6bc2d4..c263009b240c3 100644
--- a/Tests/LibCompress/TestDeflate.cpp
+++ b/Tests/LibCompress/TestDeflate.cpp
@@ -14,11 +14,7 @@
 #include <LibCore/File.h>
 #include <cstring>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibCompress/deflate-test-files/" x)
-#else
-#    define TEST_INPUT(x) ("deflate-test-files/" x)
-#endif
+#define TEST_INPUT(x) ("deflate-test-files/" x)
 
 TEST_CASE(canonical_code_simple)
 {
diff --git a/Tests/LibGfx/BenchmarkJPEGLoader.cpp b/Tests/LibGfx/BenchmarkJPEGLoader.cpp
index 1522487153a07..e97d356697ce3 100644
--- a/Tests/LibGfx/BenchmarkJPEGLoader.cpp
+++ b/Tests/LibGfx/BenchmarkJPEGLoader.cpp
@@ -8,11 +8,7 @@
 #include <LibGfx/ImageFormats/JPEGLoader.h>
 #include <LibTest/TestCase.h>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibGfx/test-inputs/" x)
-#else
-#    define TEST_INPUT(x) ("test-inputs/" x)
-#endif
+#define TEST_INPUT(x) ("test-inputs/" x)
 
 auto small_image = Core::File::open(TEST_INPUT("jpg/rgb24.jpg"sv), Core::File::OpenMode::Read).release_value()->read_until_eof().release_value();
 auto big_image = Core::File::open(TEST_INPUT("jpg/big_image.jpg"sv), Core::File::OpenMode::Read).release_value()->read_until_eof().release_value();
diff --git a/Tests/LibGfx/TestICCProfile.cpp b/Tests/LibGfx/TestICCProfile.cpp
index 3828c638d04a7..37f8c3c03db63 100644
--- a/Tests/LibGfx/TestICCProfile.cpp
+++ b/Tests/LibGfx/TestICCProfile.cpp
@@ -16,11 +16,7 @@
 #include <LibGfx/ImageFormats/WebPLoader.h>
 #include <LibTest/TestCase.h>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibGfx/test-inputs/" x)
-#else
-#    define TEST_INPUT(x) ("test-inputs/" x)
-#endif
+#define TEST_INPUT(x) ("test-inputs/" x)
 
 TEST_CASE(png)
 {
diff --git a/Tests/LibGfx/TestImageDecoder.cpp b/Tests/LibGfx/TestImageDecoder.cpp
index 75503cdd89c78..6d2bcb4433230 100644
--- a/Tests/LibGfx/TestImageDecoder.cpp
+++ b/Tests/LibGfx/TestImageDecoder.cpp
@@ -22,11 +22,7 @@
 #include <stdio.h>
 #include <string.h>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibGfx/test-inputs/" x)
-#else
-#    define TEST_INPUT(x) ("test-inputs/" x)
-#endif
+#define TEST_INPUT(x) ("test-inputs/" x)
 
 static ErrorOr<Gfx::ImageFrameDescriptor> expect_single_frame(Gfx::ImageDecoderPlugin& plugin_decoder)
 {
diff --git a/Tests/LibGfx/TestWOFF.cpp b/Tests/LibGfx/TestWOFF.cpp
index 452ca0603b5cd..2856ac3108565 100644
--- a/Tests/LibGfx/TestWOFF.cpp
+++ b/Tests/LibGfx/TestWOFF.cpp
@@ -7,11 +7,7 @@
 #include <LibGfx/Font/WOFF/Font.h>
 #include <LibTest/TestCase.h>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibGfx/test-inputs/" x)
-#else
-#    define TEST_INPUT(x) ("test-inputs/" x)
-#endif
+#define TEST_INPUT(x) ("test-inputs/" x)
 
 TEST_CASE(malformed_woff)
 {
diff --git a/Tests/LibGfx/TestWOFF2.cpp b/Tests/LibGfx/TestWOFF2.cpp
index 2cc2b2c067b17..f64b5bf6bee8c 100644
--- a/Tests/LibGfx/TestWOFF2.cpp
+++ b/Tests/LibGfx/TestWOFF2.cpp
@@ -7,11 +7,7 @@
 #include <LibGfx/Font/WOFF2/Font.h>
 #include <LibTest/TestCase.h>
 
-#ifdef AK_OS_SERENITY
-#    define TEST_INPUT(x) ("/usr/Tests/LibGfx/test-inputs/" x)
-#else
-#    define TEST_INPUT(x) ("test-inputs/" x)
-#endif
+#define TEST_INPUT(x) ("test-inputs/" x)
 
 TEST_CASE(tolerate_incorrect_sfnt_size)
 {
diff --git a/Tests/LibJS/test262-runner.cpp b/Tests/LibJS/test262-runner.cpp
index e49e4f12e8e97..57996d24d6967 100644
--- a/Tests/LibJS/test262-runner.cpp
+++ b/Tests/LibJS/test262-runner.cpp
@@ -544,17 +544,11 @@ static bool g_in_assert = false;
 // FIXME: Use a SIGABRT handler here instead of overriding internal libc assertion handlers.
 //        Fixing this will likely require updating the test driver as well to pull the assertion failure
 //        message out of stderr rather than from the json object printed to stdout.
-#ifdef AK_OS_SERENITY
-void __assertion_failed(char const* assertion)
-{
-    handle_failed_assert(assertion);
-}
-#else
-#    ifdef ASSERT_FAIL_HAS_INT /* Set by CMake */
+#ifdef ASSERT_FAIL_HAS_INT /* Set by CMake */
 extern "C" __attribute__((__noreturn__)) void __assert_fail(char const* assertion, char const* file, int line, char const* function)
-#    else
+#else
 extern "C" __attribute__((__noreturn__)) void __assert_fail(char const* assertion, char const* file, unsigned int line, char const* function)
-#    endif
+#endif
 {
     auto full_message = ByteString::formatted("{}:{}: {}: Assertion `{}' failed.", file, line, function, assertion);
     handle_failed_assert(full_message.characters());
diff --git a/Tests/LibWeb/TestHTMLTokenizer.cpp b/Tests/LibWeb/TestHTMLTokenizer.cpp
index 1bb25f3336d28..a859af123eb4b 100644
--- a/Tests/LibWeb/TestHTMLTokenizer.cpp
+++ b/Tests/LibWeb/TestHTMLTokenizer.cpp
@@ -223,12 +223,7 @@ TEST_CASE(doctype)
 //       If that changes, or something is added to the test HTML, the hash needs to be adjusted.
 TEST_CASE(regression)
 {
-    // This makes sure that the tests will run both on target and in Lagom.
-#ifdef AK_OS_SERENITY
-    StringView path = "/usr/Tests/LibWeb/tokenizer-test.html"sv;
-#else
     StringView path = "tokenizer-test.html"sv;
-#endif
 
     auto file = MUST(Core::File::open(path, Core::File::OpenMode::Read));
     auto file_size = MUST(file->size());
diff --git a/Userland/Libraries/LibCore/Command.cpp b/Userland/Libraries/LibCore/Command.cpp
index f7120b08790ce..51225fe2091a2 100644
--- a/Userland/Libraries/LibCore/Command.cpp
+++ b/Userland/Libraries/LibCore/Command.cpp
@@ -118,85 +118,4 @@ ErrorOr<Command::ProcessResult> Command::status(int options)
     return ProcessResult::Failed;
 }
 
-// Only supported in serenity mode because we use `posix_spawn_file_actions_addchdir`
-#ifdef AK_OS_SERENITY
-
-ErrorOr<CommandResult> command(ByteString const& command_string, Optional<LexicalPath> chdir)
-{
-    auto parts = command_string.split(' ');
-    if (parts.is_empty())
-        return Error::from_string_literal("empty command");
-    auto program = parts[0];
-    parts.remove(0);
-    return command(program, parts, chdir);
-}
-
-ErrorOr<CommandResult> command(ByteString const& program, Vector<ByteString> const& arguments, Optional<LexicalPath> chdir)
-{
-    int stdout_pipe[2] = {};
-    int stderr_pipe[2] = {};
-    if (pipe2(stdout_pipe, O_CLOEXEC)) {
-        return Error::from_errno(errno);
-    }
-    if (pipe2(stderr_pipe, O_CLOEXEC)) {
-        perror("pipe2");
-        return Error::from_errno(errno);
-    }
-
-    auto close_pipes = ScopeGuard([stderr_pipe, stdout_pipe] {
-        // The write-ends of these pipes are closed manually
-        close(stdout_pipe[0]);
-        close(stderr_pipe[0]);
-    });
-
-    Vector<char const*> parts = { program.characters() };
-    for (auto const& part : arguments) {
-        parts.append(part.characters());
-    }
-    parts.append(nullptr);
-
-    char const** argv = parts.data();
-
-    posix_spawn_file_actions_t action;
-    posix_spawn_file_actions_init(&action);
-    if (chdir.has_value()) {
-        posix_spawn_file_actions_addchdir(&action, chdir.value().string().characters());
-    }
-    posix_spawn_file_actions_adddup2(&action, stdout_pipe[1], STDOUT_FILENO);
-    posix_spawn_file_actions_adddup2(&action, stderr_pipe[1], STDERR_FILENO);
-
-    pid_t pid;
-    if ((errno = posix_spawnp(&pid, program.characters(), &action, nullptr, const_cast<char**>(argv), environ))) {
-        perror("posix_spawn");
-        VERIFY_NOT_REACHED();
-    }
-
-    // close the write-ends so reading wouldn't block
-    close(stdout_pipe[1]);
-    close(stderr_pipe[1]);
-
-    auto read_all_from_pipe = [](int pipe[2]) -> ErrorOr<ByteBuffer> {
-        auto result_file_or_error = Core::File::adopt_fd(pipe[0], Core::File::OpenMode::Read, Core::File::ShouldCloseFileDescriptor::Yes);
-        auto result_file = TRY(result_file_or_error);
-        return result_file->read_until_eof();
-    };
-    auto output = TRY(read_all_from_pipe(stdout_pipe));
-    auto error = TRY(read_all_from_pipe(stderr_pipe));
-
-    int wstatus { 0 };
-    waitpid(pid, &wstatus, 0);
-    posix_spawn_file_actions_destroy(&action);
-    int exit_code = WEXITSTATUS(wstatus);
-
-    if (exit_code != 0) {
-#    ifdef DBG_FAILED_COMMANDS
-        dbgln("command failed. stderr: {}", );
-#    endif
-    }
-
-    return CommandResult { WEXITSTATUS(wstatus), output, error };
-}
-
-#endif
-
 }
diff --git a/Userland/Libraries/LibCore/Environment.cpp b/Userland/Libraries/LibCore/Environment.cpp
index f0fc06a884505..1017675786a72 100644
--- a/Userland/Libraries/LibCore/Environment.cpp
+++ b/Userland/Libraries/LibCore/Environment.cpp
@@ -140,13 +140,9 @@ ErrorOr<void> unset(StringView name)
 
 ErrorOr<void> put(StringView env)
 {
-#if defined(AK_OS_SERENITY)
-    auto rc = ::serenity_putenv(env.characters_without_null_termination(), env.length());
-#else
     // Leak somewhat unavoidable here due to the putenv API.
     auto leaked_new_env = strndup(env.characters_without_null_termination(), env.length());
     auto rc = ::putenv(leaked_new_env);
-#endif
     if (rc < 0)
         return Error::from_errno(errno);
     return {};
diff --git a/Userland/Libraries/LibCore/Process.cpp b/Userland/Libraries/LibCore/Process.cpp
index 11f988b95f8d1..715ea238754c8 100644
--- a/Userland/Libraries/LibCore/Process.cpp
+++ b/Userland/Libraries/LibCore/Process.cpp
@@ -23,11 +23,7 @@
 #include <spawn.h>
 #include <unistd.h>
 
-#if defined(AK_OS_SERENITY)
-#    include <serenity.h>
-#    include <sys/prctl.h>
-#    include <syscall.h>
-#elif defined(AK_OS_BSD_GENERIC) && !defined(AK_OS_SOLARIS)
+#if defined(AK_OS_BSD_GENERIC) && !defined(AK_OS_SOLARIS)
 #    include <sys/sysctl.h>
 #elif defined(AK_OS_GNU_HURD)
 extern "C" {
@@ -84,12 +80,8 @@ ErrorOr<Process> Process::spawn(ProcessSpawnOptions const& options)
     };
 
     if (options.working_directory.has_value()) {
-#ifdef AK_OS_SERENITY
-        CHECK(posix_spawn_file_actions_addchdir(&spawn_actions, options.working_directory->characters()));
-#else
         // FIXME: Support ProcessSpawnOptions::working_directory n platforms that support it.
         TODO();
-#endif
     }
 
     for (auto const& file_action : options.file_actions) {
@@ -183,13 +175,7 @@ ErrorOr<pid_t> Process::spawn(StringView path, ReadonlySpan<char const*> argumen
 
 ErrorOr<String> Process::get_name()
 {
-#if defined(AK_OS_SERENITY)
-    char buffer[BUFSIZ];
-    int rc = get_process_name(buffer, BUFSIZ);
-    if (rc != 0)
-        return Error::from_syscall("get_process_name"sv, -rc);
-    return String::from_utf8(StringView { buffer, strlen(buffer) });
-#elif defined(AK_LIBC_GLIBC) || (defined(AK_OS_LINUX) && !defined(AK_OS_ANDROID))
+#if defined(AK_LIBC_GLIBC) || (defined(AK_OS_LINUX) && !defined(AK_OS_ANDROID))
     return String::from_utf8(StringView { program_invocation_name, strlen(program_invocation_name) });
 #elif defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
     auto const* progname = getprogname();
@@ -202,21 +188,8 @@ ErrorOr<String> Process::get_name()
 
 ErrorOr<void> Process::set_name([[maybe_unused]] StringView name, [[maybe_unused]] SetThreadName set_thread_name)
 {
-#if defined(AK_OS_SERENITY)
-    int rc = set_process_name(name.characters_without_null_termination(), name.length());
-    if (rc != 0)
-        return Error::from_syscall("set_process_name"sv, -rc);
-    if (set_thread_name == SetThreadName::No)
-        return {};
-
-    rc = prctl(PR_SET_THREAD_NAME, gettid(), name.characters_without_null_termination(), name.length());
-    if (rc != 0)
-        return Error::from_syscall("set_thread_name"sv, -rc);
-    return {};
-#else
     // FIXME: Implement Process::set_name() for other platforms.
     return {};
-#endif
 }
 
 ErrorOr<bool> Process::is_being_debugged()
@@ -327,11 +300,7 @@ void Process::wait_for_debugger_and_break()
 ErrorOr<void> Process::disown()
 {
     if (m_pid != 0 && m_should_disown) {
-#ifdef AK_OS_SERENITY
-        TRY(System::disown(m_pid));
-#else
         // FIXME: Support disown outside Serenity.
-#endif
         m_should_disown = false;
         return {};
     } else {
diff --git a/Userland/Libraries/LibCore/Socket.cpp b/Userland/Libraries/LibCore/Socket.cpp
index e2dc3b06761d1..c89b654c076cb 100644
--- a/Userland/Libraries/LibCore/Socket.cpp
+++ b/Userland/Libraries/LibCore/Socket.cpp
@@ -288,9 +288,7 @@ ErrorOr<NonnullOwnPtr<LocalSocket>> LocalSocket::adopt_fd(int fd, PreventSIGPIPE
 
 ErrorOr<int> LocalSocket::receive_fd(int flags)
 {
-#if defined(AK_OS_SERENITY)
-    return Core::System::recvfd(m_helper.fd(), flags);
-#elif defined(AK_OS_LINUX) || defined(AK_OS_GNU_HURD) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
+#if defined(AK_OS_LINUX) || defined(AK_OS_GNU_HURD) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
     union {
         struct cmsghdr cmsghdr;
         char control[CMSG_SPACE(sizeof(int))];
@@ -329,9 +327,7 @@ ErrorOr<int> LocalSocket::receive_fd(int flags)
 
 ErrorOr<void> LocalSocket::send_fd(int fd)
 {
-#if defined(AK_OS_SERENITY)
-    return Core::System::sendfd(m_helper.fd(), fd);
-#elif defined(AK_OS_LINUX) || defined(AK_OS_GNU_HURD) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
+#if defined(AK_OS_LINUX) || defined(AK_OS_GNU_HURD) || defined(AK_OS_BSD_GENERIC) || defined(AK_OS_HAIKU)
     char c = 'F';
     struct iovec iov {
         .iov_base = &c,
diff --git a/Userland/Libraries/LibCore/StandardPaths.cpp b/Userland/Libraries/LibCore/StandardPaths.cpp
index 995c992e8f75e..a15f68847408f 100644
--- a/Userland/Libraries/LibCore/StandardPaths.cpp
+++ b/Userland/Libraries/LibCore/StandardPaths.cpp
@@ -130,9 +130,7 @@ ByteString StandardPaths::data_directory()
 
     StringBuilder builder;
     builder.append(home_directory());
-#if defined(AK_OS_SERENITY)
-    builder.append("/.data"sv);
-#elif defined(AK_OS_MACOS)
+#if defined(AK_OS_MACOS)
     builder.append("/Library/Application Support"sv);
 #elif defined(AK_OS_HAIKU)
     builder.append("/config/non-packaged/data"sv);
@@ -150,10 +148,7 @@ ErrorOr<ByteString> StandardPaths::runtime_directory()
 
     StringBuilder builder;
 
-#if defined(AK_OS_SERENITY)
-    auto sid = TRY(Core::SessionManagement::root_session_id());
-    builder.appendff("/tmp/session/{}", sid);
-#elif defined(AK_OS_MACOS)
+#if defined(AK_OS_MACOS)
     builder.append(home_directory());
     builder.append("/Library/Application Support"sv);
 #elif defined(AK_OS_HAIKU)
@@ -200,9 +195,7 @@ ErrorOr<Vector<String>> StandardPaths::font_directories()
     return paths_vector;
 #else
     auto paths = Vector { {
-#    if defined(AK_OS_SERENITY)
-        "/res/fonts"_string,
-#    elif defined(AK_OS_MACOS)
+#    if defined(AK_OS_MACOS)
         "/System/Library/Fonts"_string,
         "/Library/Fonts"_string,
         TRY(String::formatted("{}/Library/Fonts"sv, home_directory())),
@@ -211,7 +204,7 @@ ErrorOr<Vector<String>> StandardPaths::font_directories()
         TRY(String::formatted("{}/X11/fonts"sv, data_directory())),
 #    endif
     } };
-#    if !(defined(AK_OS_SERENITY) || defined(AK_OS_MACOS))
+#    if !defined(AK_OS_MACOS)
     auto data_directories = Core::Environment::get("XDG_DATA_DIRS"sv).value_or("/usr/local/share:/usr/share"sv);
     TRY(data_directories.for_each_split_view(':', SplitBehavior::Nothing, [&paths](auto data_directory) -> ErrorOr<void> {
         paths.append(TRY(String::formatted("{}/fonts"sv, data_directory)));
diff --git a/Userland/Libraries/LibCore/System.cpp b/Userland/Libraries/LibCore/System.cpp
index fb8d366eaeea8..3150f4a3a86ef 100644
--- a/Userland/Libraries/LibCore/System.cpp
+++ b/Userland/Libraries/LibCore/System.cpp
@@ -27,15 +27,6 @@
 #include <termios.h>
 #include <unistd.h>
 
-#ifdef AK_OS_SERENITY
-#    include <Kernel/API/BeepInstruction.h>
-#    include <Kernel/API/Unveil.h>
-#    include <LibCore/Account.h>
-#    include <serenity.h>
-#    include <sys/ptrace.h>
-#    include <sys/sysmacros.h>
-#endif
-
 #if defined(AK_OS_LINUX) && !defined(MFD_CLOEXEC)
 #    include <linux/memfd.h>
 #    include <sys/syscall.h>
@@ -146,233 +137,6 @@ namespace Core::System {
 #    endif
 #endif
 
-#ifdef AK_OS_SERENITY
-
-ErrorOr<void> beep(u16 tone, u16 milliseconds_duration)
-{
-    static Optional<int> beep_fd;
-    if (!beep_fd.has_value())
-        beep_fd = TRY(Core::System::open("/dev/beep"sv, O_RDWR));
-    BeepInstruction instruction { tone, milliseconds_duration };
-    TRY(Core::System::write(beep_fd.value(), Span<u8 const>(&instruction, sizeof(BeepInstruction))));
-    return {};
-}
-
-ErrorOr<void> pledge(StringView promises, StringView execpromises)
-{
-    Syscall::SC_pledge_params params {
-        { promises.characters_without_null_termination(), promises.length() },
-        { execpromises.characters_without_null_termination(), execpromises.length() },
-    };
-    int rc = syscall(SC_pledge, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("pledge", rc, {});
-}
-
-static ErrorOr<void> unveil_dynamic_loader()
-{
-    static bool dynamic_loader_unveiled { false };
-    if (dynamic_loader_unveiled)
-        return {};
-    // FIXME: Try to find a way to not hardcode the dynamic loader path.
-    constexpr auto dynamic_loader_path = "/usr/lib/Loader.so"sv;
-    constexpr auto dynamic_loader_permissions = "x"sv;
-
-    Syscall::SC_unveil_params params {
-        static_cast<int>(UnveilFlags::CurrentProgram),
-        { dynamic_loader_path.characters_without_null_termination(), dynamic_loader_path.length() },
-        { dynamic_loader_permissions.characters_without_null_termination(), dynamic_loader_permissions.length() },
-    };
-    int rc = syscall(SC_unveil, &params);
-    if (rc < 0) {
-        return Error::from_syscall("unveil (DynamicLoader @ /usr/lib/Loader.so)"sv, rc);
-    }
-    dynamic_loader_unveiled = true;
-    return {};
-}
-
-ErrorOr<void> unveil(StringView path, StringView permissions)
-{
-    if (permissions.contains('x'))
-        TRY(unveil_dynamic_loader());
-
-    Syscall::SC_unveil_params params {
-        static_cast<int>(UnveilFlags::CurrentProgram),
-        { nullptr, 0 },
-        { nullptr, 0 },
-    };
-
-    ByteString parsed_path;
-    if (!path.is_null()) {
-        parsed_path = TRY(Core::SessionManagement::parse_path_with_sid(path));
-        params.path = { parsed_path.characters(), parsed_path.length() };
-        params.permissions = { permissions.characters_without_null_termination(), permissions.length() };
-    }
-
-    int rc = syscall(SC_unveil, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("unveil", rc, {});
-}
-
-ErrorOr<void> unveil_after_exec(StringView path, StringView permissions)
-{
-    ByteString parsed_path;
-    Syscall::SC_unveil_params params {
-        static_cast<int>(UnveilFlags::AfterExec),
-        { nullptr, 0 },
-        { permissions.characters_without_null_termination(), permissions.length() },
-    };
-
-    if (!path.is_null()) {
-        parsed_path = TRY(Core::SessionManagement::parse_path_with_sid(path));
-        params.path = { parsed_path.characters(), parsed_path.length() };
-    }
-
-    int rc = syscall(SC_unveil, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("unveil", rc, {});
-}
-
-ErrorOr<void> sendfd(int sockfd, int fd)
-{
-    if (::sendfd(sockfd, fd) < 0)
-        return Error::from_syscall("sendfd"sv, -errno);
-    return {};
-}
-
-ErrorOr<int> recvfd(int sockfd, int options)
-{
-    auto fd = ::recvfd(sockfd, options);
-    if (fd < 0)
-        return Error::from_syscall("recvfd"sv, -errno);
-    return fd;
-}
-
-ErrorOr<void> ptrace_peekbuf(pid_t tid, void const* tracee_addr, Bytes destination_buf)
-{
-    Syscall::SC_ptrace_buf_params buf_params {
-        { destination_buf.data(), destination_buf.size() }
-    };
-    Syscall::SC_ptrace_params params {
-        PT_PEEKBUF,
-        tid,
-        const_cast<void*>(tracee_addr),
-        (FlatPtr)&buf_params,
-    };
-    int rc = syscall(SC_ptrace, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("ptrace_peekbuf", rc, {});
-}
-
-ErrorOr<void> bindmount(int source_fd, StringView target, int flags)
-{
-    if (target.is_null())
-        return Error::from_errno(EFAULT);
-
-    Syscall::SC_bindmount_params params {
-        { target.characters_without_null_termination(), target.length() },
-        source_fd,
-        flags,
-    };
-    int rc = syscall(SC_bindmount, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("bindmount", rc, {});
-}
-
-ErrorOr<void> remount(StringView target, int flags)
-{
-    if (target.is_null())
-        return Error::from_errno(EFAULT);
-
-    Syscall::SC_remount_params params {
-        { target.characters_without_null_termination(), target.length() },
-        flags
-    };
-    int rc = syscall(SC_remount, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("remount", rc, {});
-}
-
-ErrorOr<void> mount(int source_fd, StringView target, StringView fs_type, int flags)
-{
-    if (target.is_null() || fs_type.is_null())
-        return Error::from_errno(EFAULT);
-
-    if (flags & MS_REMOUNT) {
-        TRY(remount(target, flags));
-        return {};
-    }
-    if (flags & MS_BIND) {
-        TRY(bindmount(source_fd, target, flags));
-        return {};
-    }
-    int mount_fd = TRY(fsopen(fs_type, flags));
-    return fsmount(mount_fd, source_fd, target);
-}
-
-ErrorOr<int> fsopen(StringView fs_type, int flags)
-{
-    if (fs_type.is_null())
-        return Error::from_errno(EFAULT);
-
-    Syscall::SC_fsopen_params params {
-        { fs_type.characters_without_null_termination(), fs_type.length() },
-        flags,
-    };
-    int rc = syscall(SC_fsopen, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("fsopen", rc, rc);
-}
-
-ErrorOr<void> fsmount(int mount_fd, int source_fd, StringView target)
-{
-    if (target.is_null())
-        return Error::from_errno(EFAULT);
-
-    Syscall::SC_fsmount_params params {
-        mount_fd,
-        { target.characters_without_null_termination(), target.length() },
-        source_fd,
-    };
-    int rc = syscall(SC_fsmount, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("fsmount", rc, {});
-}
-
-ErrorOr<void> umount(StringView mount_point)
-{
-    if (mount_point.is_null())
-        return Error::from_errno(EFAULT);
-
-    int rc = syscall(SC_umount, mount_point.characters_without_null_termination(), mount_point.length());
-    HANDLE_SYSCALL_RETURN_VALUE("umount", rc, {});
-}
-
-ErrorOr<long> ptrace(int request, pid_t tid, void* address, void* data)
-{
-    auto rc = ::ptrace(request, tid, address, data);
-    if (rc < 0)
-        return Error::from_syscall("ptrace"sv, -errno);
-    return rc;
-}
-
-ErrorOr<void> disown(pid_t pid)
-{
-    int rc = ::disown(pid);
-    HANDLE_SYSCALL_RETURN_VALUE("disown", rc, {});
-}
-
-ErrorOr<void> profiling_enable(pid_t pid, u64 event_mask)
-{
-    int rc = ::profiling_enable(pid, event_mask);
-    HANDLE_SYSCALL_RETURN_VALUE("profiling_enable", rc, {});
-}
-
-ErrorOr<void> profiling_disable(pid_t pid)
-{
-    int rc = ::profiling_disable(pid);
-    HANDLE_SYSCALL_RETURN_VALUE("profiling_disable", rc, {});
-}
-
-ErrorOr<void> profiling_free_buffer(pid_t pid)
-{
-    int rc = ::profiling_free_buffer(pid);
-    HANDLE_SYSCALL_RETURN_VALUE("profiling_free_buffer", rc, {});
-}
-#endif
-
 #if !defined(AK_OS_BSD_GENERIC) && !defined(AK_OS_ANDROID)
 ErrorOr<Optional<struct spwd>> getspent()
 {
@@ -443,13 +207,8 @@ ErrorOr<struct stat> fstatat(int fd, StringView path, int flags)
         return Error::from_syscall("fstatat"sv, -EFAULT);
 
     struct stat st = {};
-#ifdef AK_OS_SERENITY
-    Syscall::SC_stat_params params { { path.characters_without_null_termination(), path.length() }, &st, fd, !(flags & AT_SYMLINK_NOFOLLOW) };
-    int rc = syscall(SC_stat, &params);
-#else
     ByteString path_string = path;
     int rc = ::fstatat(fd, path_string.characters(), &st, flags);
-#endif
     HANDLE_SYSCALL_RETURN_VALUE("fstatat", rc, st);
 }
 
@@ -465,34 +224,14 @@ ErrorOr<int> fcntl(int fd, int command, ...)
     return rc;
 }
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> create_block_device(StringView name, mode_t mode, unsigned major, unsigned minor)
-{
-    return Core::System::mknod(name, mode | S_IFBLK, makedev(major, minor));
-}
-
-ErrorOr<void> create_char_device(StringView name, mode_t mode, unsigned major, unsigned minor)
-{
-    return Core::System::mknod(name, mode | S_IFCHR, makedev(major, minor));
-}
-#endif
-
 ErrorOr<void*> mmap(void* address, size_t size, int protection, int flags, int fd, off_t offset, [[maybe_unused]] size_t alignment, [[maybe_unused]] StringView name)
 {
-#ifdef AK_OS_SERENITY
-    Syscall::SC_mmap_params params { address, size, alignment, protection, flags, fd, offset, { name.characters_without_null_termination(), name.length() } };
-    ptrdiff_t rc = syscall(SC_mmap, &params);
-    if (rc < 0 && rc > -EMAXERRNO)
-        return Error::from_syscall("mmap"sv, rc);
-    return reinterpret_cast<void*>(rc);
-#else
     // NOTE: Regular POSIX mmap() doesn't support custom alignment requests.
     VERIFY(!alignment);
     auto* ptr = ::mmap(address, size, protection, flags, fd, offset);
     if (ptr == MAP_FAILED)
         return Error::from_syscall("mmap"sv, -errno);
     return ptr;
-#endif
 }
 
 ErrorOr<void> munmap(void* address, size_t size)
@@ -505,9 +244,7 @@ ErrorOr<void> munmap(void* address, size_t size)
 ErrorOr<int> anon_create([[maybe_unused]] size_t size, [[maybe_unused]] int options)
 {
     int fd = -1;
-#if defined(AK_OS_SERENITY)
-    fd = ::anon_create(round_up_to_power_of_two(size, PAGE_SIZE), options);
-#elif defined(AK_OS_LINUX) || defined(AK_OS_FREEBSD)
+#if defined(AK_OS_LINUX) || defined(AK_OS_FREEBSD)
     // FIXME: Support more options on Linux.
     auto linux_options = ((options & O_CLOEXEC) > 0) ? MFD_CLOEXEC : 0;
     fd = memfd_create("", linux_options);
@@ -569,18 +306,12 @@ ErrorOr<int> openat(int fd, StringView path, int options, mode_t mode)
 {
     if (!path.characters_without_null_termination())
         return Error::from_syscall("open"sv, -EFAULT);
-#ifdef AK_OS_SERENITY
-    Syscall::SC_open_params params { fd, { path.characters_without_null_termination(), path.length() }, options, mode };
-    int rc = syscall(SC_open, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("open", rc, rc);
-#else
     // NOTE: We have to ensure that the path is null-terminated.
     ByteString path_string = path;
     int rc = ::openat(fd, path_string.characters(), options, mode);
     if (rc < 0)
         return Error::from_syscall("open"sv, -errno);
     return rc;
-#endif
 }
 
 ErrorOr<void> close(int fd)
@@ -610,16 +341,10 @@ ErrorOr<struct stat> stat(StringView path)
         return Error::from_syscall("stat"sv, -EFAULT);
 
     struct stat st = {};
-#ifdef AK_OS_SERENITY
-    Syscall::SC_stat_params params { { path.characters_without_null_termination(), path.length() }, &st, AT_FDCWD, true };
-    int rc = syscall(SC_stat, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("stat", rc, st);
-#else
     ByteString path_string = path;
     if (::stat(path_string.characters(), &st) < 0)
         return Error::from_syscall("stat"sv, -errno);
     return st;
-#endif
 }
 
 ErrorOr<struct stat> lstat(StringView path)
@@ -629,16 +354,10 @@ ErrorOr<struct stat> lstat(StringView path)
         return Error::from_syscall("lstat"sv, -EFAULT);
 
     struct stat st = {};
-#ifdef AK_OS_SERENITY
-    Syscall::SC_stat_params params { { path.characters_without_null_termination(), path.length() }, &st, AT_FDCWD, false };
-    int rc = syscall(SC_stat, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("lstat", rc, st);
-#else
     ByteString path_string = path;
     if (::lstat(path_string.characters(), &st) < 0)
         return Error::from_syscall("lstat"sv, -errno);
     return st;
-#endif
 }
 
 ErrorOr<ssize_t> read(int fd, Bytes buffer)
@@ -770,21 +489,10 @@ ErrorOr<void> chmod(StringView pathname, mode_t mode)
     if (!pathname.characters_without_null_termination())
         return Error::from_syscall("chmod"sv, -EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_chmod_params params {
-        AT_FDCWD,
-        { pathname.characters_without_null_termination(), pathname.length() },
-        mode,
-        true
-    };
-    int rc = syscall(SC_chmod, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("chmod", rc, {});
-#else
     ByteString path = pathname;
     if (::chmod(path.characters(), mode) < 0)
         return Error::from_syscall("chmod"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> fchmod(int fd, mode_t mode)
@@ -806,16 +514,10 @@ ErrorOr<void> lchown(StringView pathname, uid_t uid, gid_t gid)
     if (!pathname.characters_without_null_termination())
         return Error::from_syscall("chown"sv, -EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_chown_params params = { { pathname.characters_without_null_termination(), pathname.length() }, uid, gid, AT_FDCWD, false };
-    int rc = syscall(SC_chown, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("chown", rc, {});
-#else
     ByteString path = pathname;
     if (::chown(path.characters(), uid, gid) < 0)
         return Error::from_syscall("chown"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid)
@@ -823,16 +525,10 @@ ErrorOr<void> chown(StringView pathname, uid_t uid, gid_t gid)
     if (!pathname.characters_without_null_termination())
         return Error::from_syscall("chown"sv, -EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_chown_params params = { { pathname.characters_without_null_termination(), pathname.length() }, uid, gid, AT_FDCWD, true };
-    int rc = syscall(SC_chown, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("chown", rc, {});
-#else
     ByteString path = pathname;
     if (::lchown(path.characters(), uid, gid) < 0)
         return Error::from_syscall("lchown"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<Optional<struct passwd>> getpwent(Span<char> buffer)
@@ -908,14 +604,9 @@ ErrorOr<Optional<struct group>> getgrnam(StringView name)
 #if !defined(AK_OS_IOS)
 ErrorOr<void> clock_settime(clockid_t clock_id, struct timespec* ts)
 {
-#    ifdef AK_OS_SERENITY
-    int rc = syscall(SC_clock_settime, clock_id, ts);
-    HANDLE_SYSCALL_RETURN_VALUE("clocksettime", rc, {});
-#    else
     if (::clock_settime(clock_id, ts) < 0)
         return Error::from_syscall("clocksettime"sv, -errno);
     return {};
-#    endif
 }
 #endif
 
@@ -1037,84 +728,50 @@ ErrorOr<bool> isatty(int fd)
 
 ErrorOr<void> link(StringView old_path, StringView new_path)
 {
-#ifdef AK_OS_SERENITY
-    Syscall::SC_link_params params {
-        .old_path = { old_path.characters_without_null_termination(), old_path.length() },
-        .new_path = { new_path.characters_without_null_termination(), new_path.length() },
-    };
-    int rc = syscall(SC_link, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("link", rc, {});
-#else
     ByteString old_path_string = old_path;
     ByteString new_path_string = new_path;
     if (::link(old_path_string.characters(), new_path_string.characters()) < 0)
         return Error::from_syscall("link"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> symlink(StringView target, StringView link_path)
 {
-#ifdef AK_OS_SERENITY
-    Syscall::SC_symlink_params params {
-        .target = { target.characters_without_null_termination(), target.length() },
-        .linkpath = { link_path.characters_without_null_termination(), link_path.length() },
-        .dirfd = AT_FDCWD,
-    };
-    int rc = syscall(SC_symlink, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("symlink", rc, {});
-#else
     ByteString target_string = target;
     ByteString link_path_string = link_path;
     if (::symlink(target_string.characters(), link_path_string.characters()) < 0)
         return Error::from_syscall("symlink"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> mkdir(StringView path, mode_t mode)
 {
     if (path.is_null())
         return Error::from_errno(EFAULT);
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_mkdir, AT_FDCWD, path.characters_without_null_termination(), path.length(), mode);
-    HANDLE_SYSCALL_RETURN_VALUE("mkdir", rc, {});
-#else
     ByteString path_string = path;
     if (::mkdir(path_string.characters(), mode) < 0)
         return Error::from_syscall("mkdir"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> chdir(StringView path)
 {
     if (path.is_null())
         return Error::from_errno(EFAULT);
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_chdir, path.characters_without_null_termination(), path.length());
-    HANDLE_SYSCALL_RETURN_VALUE("chdir", rc, {});
-#else
     ByteString path_string = path;
     if (::chdir(path_string.characters()) < 0)
         return Error::from_syscall("chdir"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> rmdir(StringView path)
 {
     if (path.is_null())
         return Error::from_errno(EFAULT);
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_rmdir, path.characters_without_null_termination(), path.length());
-    HANDLE_SYSCALL_RETURN_VALUE("rmdir", rc, {});
-#else
     ByteString path_string = path;
     if (::rmdir(path_string.characters()) < 0)
         return Error::from_syscall("rmdir"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<pid_t> fork()
@@ -1148,22 +805,11 @@ ErrorOr<void> rename(StringView old_path, StringView new_path)
     if (old_path.is_null() || new_path.is_null())
         return Error::from_errno(EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_rename_params params {
-        .olddirfd = AT_FDCWD,
-        .old_path = { old_path.characters_without_null_termination(), old_path.length() },
-        .newdirfd = AT_FDCWD,
-        .new_path = { new_path.characters_without_null_termination(), new_path.length() },
-    };
-    int rc = syscall(SC_rename, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("rename", rc, {});
-#else
     ByteString old_path_string = old_path;
     ByteString new_path_string = new_path;
     if (::rename(old_path_string.characters(), new_path_string.characters()) < 0)
         return Error::from_syscall("rename"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> unlink(StringView path)
@@ -1171,15 +817,10 @@ ErrorOr<void> unlink(StringView path)
     if (path.is_null())
         return Error::from_errno(EFAULT);
 
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_unlink, AT_FDCWD, path.characters_without_null_termination(), path.length(), 0);
-    HANDLE_SYSCALL_RETURN_VALUE("unlink", rc, {});
-#else
     ByteString path_string = path;
     if (::unlink(path_string.characters()) < 0)
         return Error::from_syscall("unlink"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> utime(StringView path, Optional<struct utimbuf> maybe_buf)
@@ -1190,15 +831,10 @@ ErrorOr<void> utime(StringView path, Optional<struct utimbuf> maybe_buf)
     struct utimbuf* buf = nullptr;
     if (maybe_buf.has_value())
         buf = &maybe_buf.value();
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_utime, path.characters_without_null_termination(), path.length(), buf);
-    HANDLE_SYSCALL_RETURN_VALUE("utime", rc, {});
-#else
     ByteString path_string = path;
     if (::utime(path_string.characters(), buf) < 0)
         return Error::from_syscall("utime"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> utimensat(int fd, StringView path, struct timespec const times[2], int flag)
@@ -1206,40 +842,6 @@ ErrorOr<void> utimensat(int fd, StringView path, struct timespec const times[2],
     if (path.is_null())
         return Error::from_errno(EFAULT);
 
-#ifdef AK_OS_SERENITY
-    // POSIX allows AT_SYMLINK_NOFOLLOW flag or no flags.
-    if (flag & ~AT_SYMLINK_NOFOLLOW)
-        return Error::from_errno(EINVAL);
-
-    // Return early without error since both changes are to be omitted.
-    if (times && times[0].tv_nsec == UTIME_OMIT && times[1].tv_nsec == UTIME_OMIT)
-        return {};
-
-    // According to POSIX, when times is a nullptr, it's equivalent to setting
-    // both last access time and last modification time to the current time.
-    // Setting the times argument to nullptr if it matches this case prevents
-    // the need to copy it in the kernel.
-    if (times && times[0].tv_nsec == UTIME_NOW && times[1].tv_nsec == UTIME_NOW)
-        times = nullptr;
-
-    if (times) {
-        for (int i = 0; i < 2; ++i) {
-            if ((times[i].tv_nsec != UTIME_NOW && times[i].tv_nsec != UTIME_OMIT)
-                && (times[i].tv_nsec < 0 || times[i].tv_nsec >= 1'000'000'000L)) {
-                return Error::from_errno(EINVAL);
-            }
-        }
-    }
-
-    Syscall::SC_utimensat_params params {
-        .dirfd = fd,
-        .path = { path.characters_without_null_termination(), path.length() },
-        .times = times,
-        .flag = flag,
-    };
-    int rc = syscall(SC_utimensat, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("utimensat", rc, {});
-#else
     auto builder = TRY(StringBuilder::create());
     TRY(builder.try_append(path));
     TRY(builder.try_append('\0'));
@@ -1248,125 +850,27 @@ ErrorOr<void> utimensat(int fd, StringView path, struct timespec const times[2],
     if (::utimensat(fd, builder.string_view().characters_without_null_termination(), times, flag) < 0)
         return Error::from_syscall("utimensat"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<struct utsname> uname()
 {
     struct utsname uts;
-#ifdef AK_OS_SERENITY
-    int rc = syscall(SC_uname, &uts);
-    HANDLE_SYSCALL_RETURN_VALUE("uname", rc, uts);
-#else
     if (::uname(&uts) < 0)
         return Error::from_syscall("uname"sv, -errno);
-#endif
     return uts;
 }
 
 #if !defined(AK_OS_ANDROID) && !defined(AK_OS_HAIKU)
 ErrorOr<void> adjtime(const struct timeval* delta, struct timeval* old_delta)
 {
-#    ifdef AK_OS_SERENITY
-    int rc = syscall(SC_adjtime, delta, old_delta);
-    HANDLE_SYSCALL_RETURN_VALUE("adjtime", rc, {});
-#    else
     if (::adjtime(delta, old_delta) < 0)
         return Error::from_syscall("adjtime"sv, -errno);
     return {};
-#    endif
-}
-#endif
-
-#ifdef AK_OS_SERENITY
-ErrorOr<void> exec_command(Vector<StringView>& command, bool preserve_env)
-{
-    Vector<StringView> exec_environment;
-    for (auto entry : Environment::entries()) {
-        // FIXME: Allow a custom selection of variables once ArgsParser supports options with optional parameters.
-        if (!preserve_env && entry.name != "TERM"sv)
-            continue;
-
-        exec_environment.append(entry.full_entry);
-    }
-
-    TRY(Core::System::exec(command.at(0), command, Core::System::SearchInPath::Yes, exec_environment));
-    return {};
-}
-
-ErrorOr<void> join_jail(u64 jail_index)
-{
-    Syscall::SC_jail_attach_params params { jail_index };
-    int rc = syscall(SC_jail_attach, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("jail_attach", rc, {});
-}
-
-ErrorOr<u64> create_jail(StringView jail_name, JailIsolationFlags flags)
-{
-    Syscall::SC_jail_create_params params { 0, { jail_name.characters_without_null_termination(), jail_name.length() }, static_cast<int>(flags) };
-    int rc = syscall(SC_jail_create, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("jail_create", rc, static_cast<u64>(params.index));
 }
 #endif
 
 ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, SearchInPath search_in_path, Optional<ReadonlySpan<StringView>> environment)
 {
-#ifdef AK_OS_SERENITY
-    Syscall::SC_execve_params params;
-
-    auto argument_strings = TRY(FixedArray<Syscall::StringArgument>::create(arguments.size()));
-    for (size_t i = 0; i < arguments.size(); ++i) {
-        argument_strings[i] = { arguments[i].characters_without_null_termination(), arguments[i].length() };
-    }
-    params.arguments.strings = argument_strings.data();
-    params.arguments.length = argument_strings.size();
-
-    size_t env_count = 0;
-    if (environment.has_value()) {
-        env_count = environment->size();
-    } else {
-        env_count = Core::Environment::size();
-    }
-
-    auto environment_strings = TRY(FixedArray<Syscall::StringArgument>::create(env_count));
-    if (environment.has_value()) {
-        for (size_t i = 0; i < env_count; ++i) {
-            environment_strings[i] = { environment->at(i).characters_without_null_termination(), environment->at(i).length() };
-        }
-    } else {
-        size_t i = 0;
-        for (auto entry : Core::Environment::entries()) {
-            environment_strings[i++] = { entry.full_entry.characters_without_null_termination(), entry.full_entry.length() };
-        }
-    }
-    params.environment.strings = environment_strings.data();
-    params.environment.length = environment_strings.size();
-
-    auto run_exec = [](Syscall::SC_execve_params& params) -> ErrorOr<void> {
-        int rc = syscall(Syscall::SC_execve, &params);
-        if (rc < 0)
-            return Error::from_syscall("exec"sv, rc);
-        return {};
-    };
-
-    StringView exec_filename;
-    String resolved_executable_path;
-    if (search_in_path == SearchInPath::Yes) {
-        auto executable_or_error = resolve_executable_from_environment(filename);
-
-        if (executable_or_error.is_error())
-            return executable_or_error.release_error();
-
-        resolved_executable_path = executable_or_error.release_value();
-        exec_filename = resolved_executable_path;
-    } else {
-        exec_filename = filename;
-    }
-
-    params.path = { exec_filename.characters_without_null_termination(), exec_filename.length() };
-    TRY(run_exec(params));
-    VERIFY_NOT_REACHED();
-#else
     ByteString filename_string { filename };
 
     auto argument_strings = TRY(FixedArray<ByteString>::create(arguments.size()));
@@ -1388,7 +892,7 @@ ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, Sear
         envp[environment->size()] = nullptr;
 
         if (search_in_path == SearchInPath::Yes && !filename.contains('/')) {
-#    if defined(AK_OS_MACOS) || defined(AK_OS_IOS) || defined(AK_OS_FREEBSD) || defined(AK_OS_SOLARIS)
+#if defined(AK_OS_MACOS) || defined(AK_OS_IOS) || defined(AK_OS_FREEBSD) || defined(AK_OS_SOLARIS)
             // These BSDs don't support execvpe(), so we'll have to manually search the PATH.
             ScopedValueRollback errno_rollback(errno);
 
@@ -1401,9 +905,9 @@ ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, Sear
 
             ByteString executable = executable_or_error.release_value().to_byte_string();
             rc = ::execve(executable.characters(), argv.data(), envp.data());
-#    else
+#else
             rc = ::execvpe(filename_string.characters(), argv.data(), envp.data());
-#    endif
+#endif
         } else {
             rc = ::execve(filename_string.characters(), argv.data(), envp.data());
         }
@@ -1418,7 +922,6 @@ ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, Sear
     if (rc < 0)
         return Error::from_syscall("exec"sv, rc);
     VERIFY_NOT_REACHED();
-#endif
 }
 
 ErrorOr<int> socket(int domain, int type, int protocol)
@@ -1628,16 +1131,10 @@ ErrorOr<void> mknod(StringView pathname, mode_t mode, dev_t dev)
     if (pathname.is_null())
         return Error::from_syscall("mknod"sv, -EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_mknod_params params { { pathname.characters_without_null_termination(), pathname.length() }, mode, dev, AT_FDCWD };
-    int rc = syscall(SC_mknod, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("mknod", rc, {});
-#else
     ByteString path_string = pathname;
     if (::mknod(path_string.characters(), mode, dev) < 0)
         return Error::from_syscall("mknod"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<void> mkfifo(StringView pathname, mode_t mode)
@@ -1674,37 +1171,17 @@ ErrorOr<void> access(StringView pathname, int mode, int flags)
     if (pathname.is_null())
         return Error::from_syscall("access"sv, -EFAULT);
 
-#ifdef AK_OS_SERENITY
-    Syscall::SC_faccessat_params params {
-        .dirfd = AT_FDCWD,
-        .pathname = { pathname.characters_without_null_termination(), pathname.length() },
-        .mode = mode,
-        .flags = flags,
-    };
-    int rc = ::syscall(Syscall::SC_faccessat, &params);
-    HANDLE_SYSCALL_RETURN_VALUE("access", rc, {});
-#else
     ByteString path_string = pathname;
     (void)flags;
     if (::access(path_string.characters(), mode) < 0)
         return Error::from_syscall("access"sv, -errno);
     return {};
-#endif
 }
 
 ErrorOr<ByteString> readlink(StringView pathname)
 {
     // FIXME: Try again with a larger buffer.
-#ifdef AK_OS_SERENITY
-    char data[PATH_MAX];
-    Syscall::SC_readlink_params small_params {
-        .path = { pathname.characters_without_null_termination(), pathname.length() },
-        .buffer = { data, sizeof(data) },
-        .dirfd = AT_FDCWD,
-    };
-    int rc = syscall(SC_readlink, &small_params);
-    HANDLE_SYSCALL_RETURN_VALUE("readlink", rc, ByteString(data, rc));
-#elif defined(AK_OS_GNU_HURD)
+#if defined(AK_OS_GNU_HURD)
     // PATH_MAX is not defined, nor is there an upper limit on path lengths.
     // Let's do this the right way.
     int fd = TRY(open(pathname, O_READ | O_NOLINK));
@@ -1731,16 +1208,6 @@ ErrorOr<int> poll(Span<struct pollfd> poll_fds, int timeout)
     return { rc };
 }
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> posix_fallocate(int fd, off_t offset, off_t length)
-{
-    int rc = ::posix_fallocate(fd, offset, length);
-    if (rc != 0)
-        return Error::from_syscall("posix_fallocate"sv, -rc);
-    return {};
-}
-#endif
-
 // This constant is copied from LibFileSystem. We cannot use or even include it directly,
 // because that would cause a dependency of LibCore on LibFileSystem, effectively rendering
 // the distinction between these libraries moot.
@@ -1784,7 +1251,7 @@ ErrorOr<String> resolve_executable_from_environment(StringView filename, int fla
 ErrorOr<ByteString> current_executable_path()
 {
     char path[4096] = {};
-#if defined(AK_OS_LINUX) || defined(AK_OS_ANDROID) || defined(AK_OS_SERENITY)
+#if defined(AK_OS_LINUX) || defined(AK_OS_ANDROID)
     auto ret = ::readlink("/proc/self/exe", path, sizeof(path) - 1);
     // Ignore error if it wasn't a symlink
     if (ret == -1 && errno != EINVAL)
diff --git a/Userland/Libraries/LibCore/System.h b/Userland/Libraries/LibCore/System.h
index 24f1f07223706..1567cdd4640f4 100644
--- a/Userland/Libraries/LibCore/System.h
+++ b/Userland/Libraries/LibCore/System.h
@@ -31,10 +31,6 @@
 #include <time.h>
 #include <utime.h>
 
-#ifdef AK_OS_SERENITY
-#    include <Kernel/API/Jail.h>
-#endif
-
 #if !defined(AK_OS_BSD_GENERIC) && !defined(AK_OS_ANDROID)
 #    include <shadow.h>
 #endif
@@ -50,32 +46,11 @@
 
 namespace Core::System {
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> beep(u16 tone = 440, u16 milliseconds_duration = 200);
-ErrorOr<void> pledge(StringView promises, StringView execpromises = {});
-ErrorOr<void> unveil(StringView path, StringView permissions);
-ErrorOr<void> unveil_after_exec(StringView path, StringView permissions);
-ErrorOr<void> sendfd(int sockfd, int fd);
-ErrorOr<int> recvfd(int sockfd, int options);
-ErrorOr<void> ptrace_peekbuf(pid_t tid, void const* tracee_addr, Bytes destination_buf);
-ErrorOr<void> mount(int source_fd, StringView target, StringView fs_type, int flags);
-ErrorOr<void> bindmount(int source_fd, StringView target, int flags);
-ErrorOr<int> fsopen(StringView fs_type, int flags);
-ErrorOr<void> fsmount(int mount_fd, int source_fd, StringView target_path);
-ErrorOr<void> remount(StringView target, int flags);
-ErrorOr<void> umount(StringView mount_point);
-ErrorOr<long> ptrace(int request, pid_t tid, void* address, void* data);
-ErrorOr<void> disown(pid_t pid);
-ErrorOr<void> profiling_enable(pid_t, u64 event_mask);
-ErrorOr<void> profiling_disable(pid_t);
-ErrorOr<void> profiling_free_buffer(pid_t);
-#else
 inline ErrorOr<void> unveil(StringView, StringView)
 {
     return {};
 }
 inline ErrorOr<void> pledge(StringView, StringView = {}) { return {}; }
-#endif
 
 template<size_t N>
 ALWAYS_INLINE ErrorOr<void> pledge(char const (&promises)[N])
@@ -201,17 +176,8 @@ enum class SearchInPath {
     Yes,
 };
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> exec_command(Vector<StringView>& command, bool preserve_env);
-#endif
-
 ErrorOr<void> exec(StringView filename, ReadonlySpan<StringView> arguments, SearchInPath, Optional<ReadonlySpan<StringView>> environment = {});
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> join_jail(u64 jail_index);
-ErrorOr<u64> create_jail(StringView jail_name, JailIsolationFlags);
-#endif
-
 ErrorOr<int> socket(int domain, int type, int protocol);
 ErrorOr<void> bind(int sockfd, struct sockaddr const*, socklen_t);
 ErrorOr<void> listen(int sockfd, int backlog);
@@ -240,11 +206,6 @@ ErrorOr<void> access(StringView pathname, int mode, int flags = 0);
 ErrorOr<ByteString> readlink(StringView pathname);
 ErrorOr<int> poll(Span<struct pollfd>, int timeout);
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> create_block_device(StringView name, mode_t mode, unsigned major, unsigned minor);
-ErrorOr<void> create_char_device(StringView name, mode_t mode, unsigned major, unsigned minor);
-#endif
-
 class AddressInfoVector {
     AK_MAKE_NONCOPYABLE(AddressInfoVector);
     AK_MAKE_DEFAULT_MOVABLE(AddressInfoVector);
@@ -277,10 +238,6 @@ class AddressInfoVector {
 
 ErrorOr<AddressInfoVector> getaddrinfo(char const* nodename, char const* servname, struct addrinfo const& hints);
 
-#ifdef AK_OS_SERENITY
-ErrorOr<void> posix_fallocate(int fd, off_t offset, off_t length);
-#endif
-
 unsigned hardware_concurrency();
 
 ErrorOr<String> resolve_executable_from_environment(StringView filename, int flags = 0);
diff --git a/Userland/Libraries/LibCore/Version.cpp b/Userland/Libraries/LibCore/Version.cpp
index 2f7d3c0dbd8cd..8f5b646c734a9 100644
--- a/Userland/Libraries/LibCore/Version.cpp
+++ b/Userland/Libraries/LibCore/Version.cpp
@@ -7,27 +7,11 @@
 #include <AK/String.h>
 #include <LibCore/Version.h>
 
-#ifdef AK_OS_SERENITY
-#    include <sys/utsname.h>
-#endif
-
 namespace Core::Version {
 
 ErrorOr<String> read_long_version_string()
 {
-#ifdef AK_OS_SERENITY
-    struct utsname uts;
-    int rc = uname(&uts);
-    if ((rc) < 0) {
-        return Error::from_syscall("uname"sv, rc);
-    }
-    auto const* version = uts.release;
-    auto const* git_hash = uts.version;
-
-    return String::formatted("Version {} revision {}", version, git_hash);
-#else
     return "Version 1.0"_string;
-#endif
 }
 
 }
diff --git a/Userland/Libraries/LibWeb/Loader/UserAgent.h b/Userland/Libraries/LibWeb/Loader/UserAgent.h
index ad75fd8928fed..8ada7e2d5dc9b 100644
--- a/Userland/Libraries/LibWeb/Loader/UserAgent.h
+++ b/Userland/Libraries/LibWeb/Loader/UserAgent.h
@@ -23,9 +23,7 @@ namespace Web {
 #    error Unknown architecture
 #endif
 
-#if defined(AK_OS_SERENITY)
-#    define OS_STRING "SerenityOS"
-#elif defined(AK_OS_ANDROID)
+#if defined(AK_OS_ANDROID)
 #    define OS_STRING "Android 10"
 #elif defined(AK_OS_LINUX)
 #    define OS_STRING "Linux"