diff --git a/.github/workflows/tox.yml b/.github/workflows/tox.yml
index e436b4ca..8f691e32 100644
--- a/.github/workflows/tox.yml
+++ b/.github/workflows/tox.yml
@@ -67,3 +67,45 @@ jobs:
           else
             python -m tox run -e py311-${{ matrix.toxenv }}
           fi
+  tox-pypy:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python: ['pypy3.9', 'pypy3.10']
+        toxenv: [core, wheel]
+      fail-fast: false
+    steps:
+      - env:
+          python: ${{ matrix.python }}
+          toxenv: ${{ matrix.toxenv }}
+        run: |
+          echo "TOXENV=${python}-${toxenv}" | tr -d '.' | tee -a $GITHUB_ENV
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python }}
+      - run: |
+          python -m pip install --upgrade pip
+          python -m pip install tox
+          python -m pip install --no-binary :all: cffi
+
+      # - run: |
+      #     python -m tox run -r
+      - run: |
+          # Write sitecustomize.py that patches _cffi_backend
+          mkdir -p .ci-pypy-patch
+          cat <<EOF > .ci-pypy-patch/sitecustomize.py
+          import sys
+          try:
+              import _cffi_backend
+              if not hasattr(_cffi_backend, '__file__'):
+                  _cffi_backend.__file__ = "/usr/lib/libcffi.so"  # dummy fallback path
+          except (ImportError, AttributeError):
+              pass
+          EOF
+
+          # Set PYTHONPATH to load the patch
+          export PYTHONPATH="$PWD/.ci-pypy-patch"
+
+          # Run tox
+          python -m tox run -r
diff --git a/newsfragments/505.internal.rst b/newsfragments/505.internal.rst
new file mode 100644
index 00000000..4a8a3bbf
--- /dev/null
+++ b/newsfragments/505.internal.rst
@@ -0,0 +1 @@
+Adds ``pypy3.9`` and ``pypy3.10`` to CI checks.
diff --git a/setup.py b/setup.py
index 85a4b302..b1811130 100644
--- a/setup.py
+++ b/setup.py
@@ -101,6 +101,9 @@
         "Programming Language :: Python :: 3.11",
         "Programming Language :: Python :: 3.12",
         "Programming Language :: Python :: 3.13",
+        "Programming Language :: Python :: Implementation :: PyPy",
+        "Programming Language :: Python :: Implementation :: PyPy :: 3.9",
+        "Programming Language :: Python :: Implementation :: PyPy :: 3.10",
     ],
     platforms=["unix", "linux", "osx", "win32"],
     entry_points={
diff --git a/tox.ini b/tox.ini
index 983c3ee4..33940671 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,8 +1,10 @@
 [tox]
 envlist=
     py{39,310,311,312,313}-core
+    pypy{39,310}-core
     py{39,310,311,312,313}-lint
     py{39,310,311,312,313}-wheel
+    pypy{39,310}-wheel
     py{39,310,311,312,313}-interop
     windows-wheel
     docs
@@ -31,6 +33,8 @@ basepython=
     py311: python3.11
     py312: python3.12
     py313: python3.13
+    pypy39: pypy3.9
+    pypy310: pypy3.10
 extras=
     test
     docs
@@ -44,7 +48,7 @@ commands=
     pre-commit install
     pre-commit run --all-files --show-diff-on-failure
 
-[testenv:py{39,310,311,312,313}-wheel]
+[testenv:py{39,310,311,312,313,py39,py310}-wheel]
 deps=
     wheel
     build[virtualenv]