diff --git a/pyproject.toml b/pyproject.toml
index b7823b3..dabd973 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -18,6 +18,7 @@ classifiers = [
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
+    "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     "Topic :: Security :: Cryptography",
diff --git a/tox.ini b/tox.ini
index f3015ba..429c151 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@ env_list =
     lint,
     mypy-{api,pkg},
     docs,
-    py3{8,9,10,11,12}{,-pyopenssl}{,-oldest}{,-idna},
+    py3{8,9,10,11,12,13}{,-pyopenssl}{,-oldest}{,-idna},
     coverage-report