diff --git a/pyproject.toml b/pyproject.toml
index dcedca1..ec2fd8f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,7 +18,7 @@ classifiers = [
   "Programming Language :: Python :: 3.14",
   "Topic :: Software Development",
 ]
-requires-python = ">=3.9"
+requires-python = ">=3.10"
 dependencies = [
   "aiohttp[speedups]~=3.8",
   "gql[aiohttp,requests]>=4,<5",
@@ -72,7 +72,7 @@ select = [
 ignore = [
     "E501",  # let black handle line-length
 ]
-target-version = "py38"
+target-version = "py310"
 
 [tool.ruff.isort]
 known-first-party = ["simple_github"]
diff --git a/src/simple_github/__init__.py b/src/simple_github/__init__.py
index 154775c..7661381 100644
--- a/src/simple_github/__init__.py
+++ b/src/simple_github/__init__.py
@@ -1,13 +1,12 @@
 import asyncio
 import os
 from functools import partial
-from typing import List, Optional, Union
 
 from .auth import AppAuth, AppInstallationAuth, PublicAuth, TokenAuth
 from .client import AsyncClient, Client, SyncClient
 
 
-def client_from_env(owner: str, repositories: List[str]):
+def client_from_env(owner: str, repositories: list[str]):
     if "GITHUB_TOKEN" in os.environ:
         return partial(TokenClient, os.environ["GITHUB_TOKEN"])
     elif "GITHUB_APP_ID" in os.environ and "GITHUB_APP_PRIVKEY" in os.environ:
@@ -25,8 +24,8 @@ def client_from_env(owner: str, repositories: List[str]):
 def AppClient(
     id: int,
     privkey: str,
-    owner: Optional[str] = None,
-    repositories: Optional[Union[List[str], str]] = None,
+    owner: str | None = None,
+    repositories: list[str] | str | None = None,
 ) -> Client:
     """Convenience function to create a `Client` instance authenticated
     as a Github App.
@@ -41,7 +40,7 @@ def AppClient(
         owner (str): The org or user where the app is installed. If not
             specified, the returned client will be authenticated as the app
             itself rather than as an app installation.
-        repositories (List[str]): A list of repositories to limit the app's
+        repositories (list[str]): A list of repositories to limit the app's
             scope to. If not specified, the client will have access to all
             repositories owned by `owner`.
 
diff --git a/src/simple_github/auth.py b/src/simple_github/auth.py
index 4a8f8da..d6037f8 100644
--- a/src/simple_github/auth.py
+++ b/src/simple_github/auth.py
@@ -1,6 +1,7 @@
 import time
 from abc import ABC, abstractmethod
-from typing import Any, AsyncGenerator, AsyncIterator, List, Optional, Union
+from collections.abc import AsyncGenerator, AsyncIterator
+from typing import Any
 
 import jwt
 
@@ -105,7 +106,7 @@ def __init__(
         self,
         app: AppAuth,
         owner: str,
-        repositories: Optional[Union[List[str], str]] = None,
+        repositories: list[str] | str | None = None,
     ):
         """Authentication for a Github App installation.
 
diff --git a/src/simple_github/client.py b/src/simple_github/client.py
index 13b59f8..057b56f 100644
--- a/src/simple_github/client.py
+++ b/src/simple_github/client.py
@@ -1,7 +1,8 @@
 import asyncio
 import json
 from abc import abstractmethod
-from typing import TYPE_CHECKING, Any, Coroutine, Dict, Optional, Union
+from collections.abc import Coroutine
+from typing import TYPE_CHECKING, Any
 
 from aiohttp import ClientResponse, ClientSession
 from gql import Client as GqlClient
@@ -18,13 +19,13 @@
 GITHUB_API_ENDPOINT = "https://api.github.com"
 GITHUB_GRAPHQL_ENDPOINT = "https://api.github.com/graphql"
 
-Response = Union[RequestsResponse, ClientResponse]
-RequestData = Optional[Dict[str, Any]]
+Response = RequestsResponse | ClientResponse
+RequestData = dict[str, Any] | None
 
 # Implementations of the base class can be either sync or async.
-BaseDict = Union[Dict[str, Any], Coroutine[None, None, Dict[str, Any]]]
-BaseNone = Union[None, Coroutine[None, None, None]]
-BaseResponse = Union[Response, Coroutine[None, None, Response]]
+BaseDict = dict[str, Any] | Coroutine[None, None, dict[str, Any]]
+BaseNone = None | Coroutine[None, None, None]
+BaseResponse = Response | Coroutine[None, None, Response]
 
 
 class Client:
@@ -40,10 +41,10 @@ def __init__(self, auth: "Auth"):
         """
         self.auth = auth
         self._prev_token = None
-        self._gql_client: Optional[GqlClient] = None
-        self._gql_session: Optional[
-            Any[ReconnectingAsyncClientSession, SyncClientSession]
-        ] = None
+        self._gql_client: GqlClient | None = None
+        self._gql_session: (
+            Any[ReconnectingAsyncClientSession, SyncClientSession] | None
+        ) = None
 
     @abstractmethod
     def close(self) -> BaseNone: ...
@@ -196,7 +197,7 @@ def delete(self, query: str, data: RequestData = None) -> None:
         """
         self.request("DELETE", query, data=json.dumps(data))
 
-    def execute(self, query: str, variables: RequestData = None) -> Dict[str, Any]:
+    def execute(self, query: str, variables: RequestData = None) -> dict[str, Any]:
         """Execute a query against Github's GraphQL endpoint.
 
         Args:
@@ -340,7 +341,7 @@ async def delete(self, query: str, data: RequestData = None) -> None:
 
     async def execute(
         self, query: str, variables: RequestData = None
-    ) -> Dict[str, Any]:
+    ) -> dict[str, Any]:
         """Execute a query against Github's GraphQL endpoint.
 
         Args:
diff --git a/taskcluster/kinds/docker-image/kind.yml b/taskcluster/kinds/docker-image/kind.yml
index b804e05..7a833cd 100644
--- a/taskcluster/kinds/docker-image/kind.yml
+++ b/taskcluster/kinds/docker-image/kind.yml
@@ -10,5 +10,5 @@ tasks:
     fetch: {}
     python:
         args:
-            PYTHON_VERSIONS: "3.14 3.13 3.12 3.11 3.10 3.9"
+            PYTHON_VERSIONS: "3.14 3.13 3.12 3.11 3.10"
             UV_VERSION: 0.9.18