diff --git a/.changeset/legal-camels-poke.md b/.changeset/legal-camels-poke.md
new file mode 100644
index 000000000000..fd1c897ce7dc
--- /dev/null
+++ b/.changeset/legal-camels-poke.md
@@ -0,0 +1,5 @@
+---
+'astro': minor
+---
+
+Ensure Astro.url.pathname returns the correct file extension when build.format.preserved is enabled
diff --git a/packages/astro/src/core/build/generate.ts b/packages/astro/src/core/build/generate.ts
index 511484bb17e7..b66b002e24c0 100644
--- a/packages/astro/src/core/build/generate.ts
+++ b/packages/astro/src/core/build/generate.ts
@@ -467,7 +467,12 @@ function getUrlForPath(
 	switch (format) {
 		case 'directory':
 		case 'preserve': {
-			ending = trailingSlash === 'never' ? '' : '/';
+			const isNamedPathnameRegex = /\/[a-zA-Z-0-9]+/;
+			if (isNamedPathnameRegex.test(pathname)) {
+				ending = '.html'
+			} else {
+				ending = trailingSlash === 'never' ? '' : '/';
+			}
 			break;
 		}
 		case 'file':