diff --git a/pyproject.toml b/pyproject.toml
index 024a16023..5212fcc3c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -21,6 +21,7 @@ classifiers = [
   "Programming Language :: Python :: 3.11",
   "Programming Language :: Python :: 3.12",
   "Programming Language :: Python :: 3.13",
+  "Programming Language :: Python :: 3.14",
   "Programming Language :: Python :: Implementation :: CPython",
   "Programming Language :: Python :: Implementation :: PyPy",
   "Typing :: Typed",
@@ -30,7 +31,8 @@ dynamic = ["version", "readme"]
 
 [project.optional-dependencies]
 tests-mypy = [
-  'pytest-mypy-plugins; platform_python_implementation == "CPython" and python_version >= "3.10"',
+  # A transitive dependency of pytest-mypy-plugins doesn't build on 3.14 yet.
+  'pytest-mypy-plugins; platform_python_implementation == "CPython" and python_version >= "3.10" and python_version < "3.14"',
   # Since the mypy error messages keep changing, we have to keep updating this
   # pin.
   'mypy>=1.11.1; platform_python_implementation == "CPython" and python_version >= "3.10"',
diff --git a/tox.ini b/tox.ini
index 585c3c7c9..1ca8e2f24 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,8 +1,9 @@
 [tox]
 min_version = 4
+# Mypy doesn't run on 3.14 yet.
 env_list =
     pre-commit,
-    py3{8,9,10,11,12,13}-tests,
+    py3{8,9,10,11,12,13,14}-tests,
     py3{10,11,12,13}-mypy,
     pypy3-tests,
     pyright,