diff --git a/.github/workflows/docker/shared.env b/.github/workflows/docker/shared.env
index c10e471..2929d0f 100644
--- a/.github/workflows/docker/shared.env
+++ b/.github/workflows/docker/shared.env
@@ -1,6 +1,6 @@
 PYTHON_VERSIONS=(
+    cp313-cp313
     cp312-cp312
     cp311-cp311
     cp310-cp310
-    cp39-cp39
 )
diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index e331466..5ed2c53 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -16,7 +16,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        python: [ 3.9, 3.12 ]
+        python: [ "3.10", 3.13 ]
         os:  [ macos-latest, ubuntu-24.04, windows-latest ]
     defaults:
       run:
diff --git a/.github/workflows/wheels.yml b/.github/workflows/wheels.yml
index 514ca58..ac2258a 100644
--- a/.github/workflows/wheels.yml
+++ b/.github/workflows/wheels.yml
@@ -53,7 +53,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        python: [3.9, "3.10", 3.11, 3.12]
+        python: ["3.10", 3.11, 3.12, 3.13]
     steps:
       - name: Download wheels
         uses: actions/download-artifact@v4.2.0
@@ -75,7 +75,7 @@ jobs:
     runs-on: windows-latest
     strategy:
       matrix:
-        python: [3.9, "3.10", 3.11, 3.12]
+        python: ["3.10", 3.11, 3.12, 3.13]
         wordsize: [64]
     steps:
       - name: Download wheels
@@ -99,7 +99,7 @@ jobs:
     needs: ['manylinux']
     strategy:
       matrix:
-        python: [3.9, "3.10", 3.11, 3.12]
+        python: ["3.10", 3.11, 3.12, 3.13]
     steps:
       - name: Download wheels
         uses: actions/download-artifact@v4.2.0
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 3d6d51f..9c84866 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,3 +1,9 @@
+--------------------
+[0.2.5] - 2025-XX-XX
+--------------------
+
+- Drop Python 3.9 support, require Python >= 3.10 (#112, benjeffery)
+
 --------------------
 [0.2.4] - 2024-07-10
 --------------------
diff --git a/pyproject.toml b/pyproject.toml
index fbaeac1..a00ed06 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,15 +9,15 @@ authors = [
 ]
 description = "Compression utilities for tree sequences"
 readme = "README.md"
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 license = {text = "MIT"}
 classifiers = [
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3 :: Only",
     "Development Status :: 5 - Production/Stable",
     "Environment :: Other Environment",