diff --git a/.github/workflows/docker-gdal.yml b/.github/workflows/docker-gdal.yml
index de600454..864457b7 100644
--- a/.github/workflows/docker-gdal.yml
+++ b/.github/workflows/docker-gdal.yml
@@ -26,8 +26,8 @@ jobs:
           - "ghcr.io/osgeo/gdal:ubuntu-small-3.8.5" # python 3.10.12
           - "ghcr.io/osgeo/gdal:ubuntu-small-3.7.3" # python 3.10.12
           - "ghcr.io/osgeo/gdal:ubuntu-small-3.6.4" # python 3.10.6
-          - "osgeo/gdal:ubuntu-small-3.5.3" # python 3.9.20 (installed manually)
-          - "osgeo/gdal:ubuntu-small-3.4.3" # python 3.9.20 (installed manually)
+          - "osgeo/gdal:ubuntu-small-3.5.3" # python 3.10 (installed manually)
+          - "osgeo/gdal:ubuntu-small-3.4.3" # python 3.10 (installed manually)
 
     container:
       image: ${{ matrix.container }}
@@ -44,7 +44,7 @@ jobs:
         run: |
           apt-get update && apt-get install -y software-properties-common
           add-apt-repository -y ppa:deadsnakes/ppa
-          apt-get update && apt-get install -y python3.9-dev
+          apt-get update && apt-get install -y python3.10-dev
 
       - uses: actions/checkout@v5
 
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 978fd653..b662cf0d 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -257,7 +257,7 @@ jobs:
             "macos-13",
             "macos-latest",
           ]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
         include:
           - os: "ubuntu-latest"
             artifact: pyogrio-wheel-linux-manylinux2014_x86_64
diff --git a/.github/workflows/tests-conda.yml b/.github/workflows/tests-conda.yml
index d74a2c5d..259dc620 100644
--- a/.github/workflows/tests-conda.yml
+++ b/.github/workflows/tests-conda.yml
@@ -33,7 +33,7 @@ jobs:
               geopandas=0.12
           # minimal environment without optional dependencies
           - os: "ubuntu-latest"
-            python: "3.9"
+            python: "3.10"
             env: "minimal"
           # environment for older Windows libgdal to make sure gdal_i.lib is
           # properly detected
diff --git a/CHANGES.md b/CHANGES.md
index 9e786442..c34f6734 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,10 +1,14 @@
 # CHANGELOG
 
-## 0.12.0 (yyyy-mm-dd)
+## 0.12.0 (xxxx-xx-xx)
+
+### Packaging
+
+-   pyogrio now requires a minimum version of Python >= 3.10 (#557).
 
 ### Bug fixes
 
--   Fix wrong layername when creating .gpkg.zip file (#570)
+-   Fix wrong layername when creating .gpkg.zip file (#570).
 
 ## 0.11.1 (2025-08-02)
 
diff --git a/README.md b/README.md
index 9e5e9708..75de1530 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ Read the documentation for more information:
 
 ## Requirements
 
-Supports Python 3.9 - 3.13 and GDAL 3.4.x - 3.9.x.
+Supports Python 3.10 - 3.13 and GDAL 3.4.x - 3.9.x.
 
 Reading to GeoDataFrames requires `geopandas>=0.12` with `shapely>=2`.
 
diff --git a/docs/environment.yml b/docs/environment.yml
index af811239..0c3679c7 100644
--- a/docs/environment.yml
+++ b/docs/environment.yml
@@ -2,9 +2,9 @@ name: pyogrio
 channels:
   - conda-forge
 dependencies:
-  - python==3.9.*
+  - python==3.10.*
   - gdal
-  - numpy==1.19.*
+  - numpy==1.24.*
   - numpydoc==1.1.*
   - Cython==0.29.*
   - docutils==0.16.*
diff --git a/docs/source/install.md b/docs/source/install.md
index 94513d11..61a4fdb9 100644
--- a/docs/source/install.md
+++ b/docs/source/install.md
@@ -2,7 +2,7 @@
 
 ## Requirements
 
-Supports Python 3.9 - 3.13 and GDAL 3.4.x - 3.9.x
+Supports Python 3.10 - 3.13 and GDAL 3.4.x - 3.9.x
 
 Reading to GeoDataFrames requires `geopandas>=0.12` with `shapely>=2`.
 
diff --git a/pyogrio/core.py b/pyogrio/core.py
index 1fa18fa4..e06418c0 100644
--- a/pyogrio/core.py
+++ b/pyogrio/core.py
@@ -1,7 +1,6 @@
 """Core functions to interact with OGR data sources."""
 
 from pathlib import Path
-from typing import Optional, Union
 
 from pyogrio._env import GDALEnv
 from pyogrio.util import (
@@ -336,7 +335,7 @@ def get_gdal_data_path():
     return _get_gdal_data_path()
 
 
-def vsi_listtree(path: Union[str, Path], pattern: Optional[str] = None):
+def vsi_listtree(path: str | Path, pattern: str | None = None):
     """Recursively list the contents of a VSI directory.
 
     An fnmatch pattern can be specified to filter the directories/files
@@ -356,7 +355,7 @@ def vsi_listtree(path: Union[str, Path], pattern: Optional[str] = None):
     return ogr_vsi_listtree(path, pattern=pattern)
 
 
-def vsi_rmtree(path: Union[str, Path]):
+def vsi_rmtree(path: str | Path):
     """Recursively remove VSI directory.
 
     Parameters
@@ -371,7 +370,7 @@ def vsi_rmtree(path: Union[str, Path]):
     ogr_vsi_rmtree(path)
 
 
-def vsi_unlink(path: Union[str, Path]):
+def vsi_unlink(path: str | Path):
     """Remove a VSI file.
 
     Parameters
diff --git a/pyogrio/geopandas.py b/pyogrio/geopandas.py
index ce57575b..810f6e7a 100644
--- a/pyogrio/geopandas.py
+++ b/pyogrio/geopandas.py
@@ -697,7 +697,7 @@ def write_dataframe(
         if isinstance(values, pd.api.extensions.ExtensionArray):
             from pandas.arrays import BooleanArray, FloatingArray, IntegerArray
 
-            if isinstance(values, (IntegerArray, FloatingArray, BooleanArray)):
+            if isinstance(values, IntegerArray | FloatingArray | BooleanArray):
                 field_data.append(values._data)
                 field_mask.append(values._mask)
             else:
diff --git a/pyogrio/util.py b/pyogrio/util.py
index 0c8e4399..0479df89 100644
--- a/pyogrio/util.py
+++ b/pyogrio/util.py
@@ -4,7 +4,6 @@
 import sys
 from packaging.version import Version
 from pathlib import Path
-from typing import Union
 from urllib.parse import urlparse
 
 from pyogrio._ogr import MULTI_EXTENSIONS
@@ -53,7 +52,7 @@ def get_vsi_path_or_buffer(path_or_buffer):
     return vsi_path(str(path_or_buffer))
 
 
-def vsi_path(path: Union[str, Path]) -> str:
+def vsi_path(path: str | Path) -> str:
     """Ensure path is a local path or a GDAL-compatible VSI path."""
     # Convert Path objects to string, but for VSI paths, keep posix style path.
     if isinstance(path, Path):
@@ -236,7 +235,7 @@ def _mask_to_wkb(mask):
     return shapely.to_wkb(mask)
 
 
-def vsimem_rmtree_toplevel(path: Union[str, Path]):
+def vsimem_rmtree_toplevel(path: str | Path):
     """Remove the parent directory of the file path recursively.
 
     This is used for final cleanup of an in-memory dataset, which may have been
diff --git a/pyproject.toml b/pyproject.toml
index d4d1640b..a86f467f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -27,7 +27,7 @@ classifiers = [
     "Programming Language :: Python :: 3",
     "Topic :: Scientific/Engineering :: GIS",
 ]
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 dependencies = ["certifi", "numpy", "packaging"]
 
 [project.optional-dependencies]
diff --git a/setup.py b/setup.py
index 10c4a03d..6a3ffd74 100644
--- a/setup.py
+++ b/setup.py
@@ -20,12 +20,12 @@
 logger = logging.getLogger(__name__)
 
 
-MIN_PYTHON_VERSION = (3, 9, 0)
+MIN_PYTHON_VERSION = (3, 10, 0)
 MIN_GDAL_VERSION = (2, 4, 0)
 
 
 if sys.version_info < MIN_PYTHON_VERSION:
-    raise RuntimeError("Python >= 3.9 is required")
+    raise RuntimeError("Python >= 3.10 is required")
 
 
 def copy_data_tree(datadir, destdir):