diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 84496648..cadb14f2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,6 +6,18 @@ on:
   pull_request: {}
 
 jobs:
+  mypy:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Set up Python
+        uses: actions/setup-python@v2
+      - name: Install dependencies
+        run: pip install mypy
+      - name: Run mypy
+        run: mypy --strict certifi
+
   test:
     runs-on: ubuntu-latest
     strategy:
diff --git a/certifi/__init__.py b/certifi/__init__.py
index 8db1a0e5..41a722e4 100644
--- a/certifi/__init__.py
+++ b/certifi/__init__.py
@@ -1,3 +1,4 @@
 from .core import contents, where
 
+__all__ = ["contents", "where"]
 __version__ = "2021.10.08"
diff --git a/certifi/core.py b/certifi/core.py
index 5d2b8cd3..d768be79 100644
--- a/certifi/core.py
+++ b/certifi/core.py
@@ -7,6 +7,8 @@
 This module returns the installation location of cacert.pem or its contents.
 """
 import os
+import types
+from typing import Union
 
 try:
     from importlib.resources import path as get_path, read_text
@@ -14,7 +16,7 @@
     _CACERT_CTX = None
     _CACERT_PATH = None
 
-    def where():
+    def where() -> str:
         # This is slightly terrible, but we want to delay extracting the file
         # in cases where we're inside of a zipimport situation until someone
         # actually calls where(), but we don't want to re-extract the file
@@ -40,21 +42,29 @@ def where():
 
 
 except ImportError:
+    Package = Union[types.ModuleType, str]
+    Resource = Union[str, "os.PathLike"]
+
     # This fallback will work for Python versions prior to 3.7 that lack the
     # importlib.resources module but relies on the existing `where` function
     # so won't address issues with environments like PyOxidizer that don't set
     # __file__ on modules.
-    def read_text(_module, _path, encoding="ascii"):
+    def read_text(
+        package: Package,
+        resource: Resource,
+        encoding: str = 'utf-8',
+        errors: str = 'strict'
+    ) -> str:
         with open(where(), "r", encoding=encoding) as data:
             return data.read()
 
     # If we don't have importlib.resources, then we will just do the old logic
     # of assuming we're on the filesystem and munge the path directly.
-    def where():
+    def where() -> str:
         f = os.path.dirname(__file__)
 
         return os.path.join(f, "cacert.pem")
 
 
-def contents():
+def contents() -> str:
     return read_text("certifi", "cacert.pem", encoding="ascii")
diff --git a/certifi/py.typed b/certifi/py.typed
new file mode 100644
index 00000000..e69de29b
diff --git a/certifi/tests/test_certify.py b/certifi/tests/test_certify.py
index 7fb8c77f..4b443f27 100755
--- a/certifi/tests/test_certify.py
+++ b/certifi/tests/test_certify.py
@@ -7,9 +7,14 @@
 
 
 class TestCertifi(unittest.TestCase):
-    def test_cabundle_exists(self):
+    def test_cabundle_exists(self) -> None:
         assert os.path.exists(certifi.where())
 
-    def test_read_contents(self):
+    def test_read_contents(self) -> None:
         content = certifi.contents()
         assert "-----BEGIN CERTIFICATE-----" in content
+
+    def test_py_typed_exists(self) -> None:
+        assert os.path.exists(
+            os.path.join(os.path.dirname(certifi.__file__), 'py.typed')
+        )
diff --git a/setup.py b/setup.py
index c3519635..48dc8912 100755
--- a/setup.py
+++ b/setup.py
@@ -43,7 +43,7 @@
         'certifi',
     ],
     package_dir={'certifi': 'certifi'},
-    package_data={'certifi': ['*.pem']},
+    package_data={'certifi': ['*.pem', 'py.typed']},
     # data_files=[('certifi', ['certifi/cacert.pem'])],
     include_package_data=True,
     zip_safe=False,