diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index ec53e1c..52c069b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -16,42 +16,62 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
-
   format:
     name: "Check formatting"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      # [[[cog cog.include("./steps/checkout.yml") ]]]
+      - name: "Check out the repo"
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
+      # [[[end]]]
 
+      # [[[cog cog.include("./steps/ruff.yml") ]]]
       - uses: astral-sh/ruff-action@eaf0ecdd668ceea36159ff9d91882c9795d89b49 # v3.4.0
+        # [[[end]]]
         with:
-          args: 'format --check'
+          args: "format --check"
 
   lint:
     name: "Lint"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+      # [[[cog cog.include("./steps/checkout.yml") ]]]
+      - name: "Check out the repo"
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
+      # [[[end]]]
 
+      # [[[cog cog.include("./steps/ruff.yml") ]]]
       - uses: astral-sh/ruff-action@eaf0ecdd668ceea36159ff9d91882c9795d89b49 # v3.4.0
+      # [[[end]]]
 
+      # [[[cog cog.include("./steps/setup-python.yml") ]]]
       - name: "Set up Python"
         uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        # [[[end]]]
         with:
           python-version: "3.13"
 
+      # [[[cog cog.include("./steps/install-dependencies.yml") ]]]
       - name: "Install dependencies"
         run: |
           python -m pip install -r requirements.pip
-
+      # [[[end]]]
       - name: "Check the docs are up-to-date"
         run: |
           make lintdoc
 
+      - name: "Check that this file is up-to-date"
+        run: |
+          python -m cogapp -r --check --diff .github/workflows/ci.yml
+          if [ $? -ne 0 ]; then
+            echo 'Docs need to be updated: `python -m cogapp -r .github/workflows/ci.yml`';
+            exit 1;
+          fi
+
   tests:
     name: "Python ${{ matrix.python }} on ${{ matrix.os }}"
     runs-on: "${{ matrix.os }}-${{ matrix.os-version || 'latest' }}"
@@ -79,20 +99,25 @@ jobs:
             os-version: "13"
 
     steps:
+      # [[[cog cog.include("./steps/checkout.yml") ]]]
       - name: "Check out the repo"
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
           persist-credentials: false
+      # [[[end]]]
 
+      # [[[cog cog.include("./steps/setup-python.yml") ]]]
       - name: "Set up Python"
         uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        # [[[end]]]
         with:
           python-version: "${{ matrix.python }}"
 
+      # [[[cog cog.include("./steps/install-dependencies.yml") ]]]
       - name: "Install dependencies"
         run: |
           python -m pip install -r requirements.pip
-
+      # [[[end]]]
       - name: "Run tox for ${{ matrix.python }}"
         run: |
           python -m tox
@@ -111,21 +136,26 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
+      # [[[cog cog.include("./steps/checkout.yml") ]]]
       - name: "Check out the repo"
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          fetch-depth: "0"
           persist-credentials: false
+          # [[[end]]]
+          fetch-depth: "0"
 
+      # [[[cog cog.include("./steps/setup-python.yml") ]]]
       - name: "Set up Python"
         uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
+        # [[[end]]]
         with:
           python-version: "3.9"
 
+      # [[[cog cog.include("./steps/install-dependencies.yml") ]]]
       - name: "Install dependencies"
         run: |
           python -m pip install -r requirements.pip
-
+      # [[[end]]]
       - name: "Download coverage data"
         uses: actions/download-artifact@d3f86a106a0bac45b974a628896c90dbdf5c8093 # v4.3.0
         with:
diff --git a/.github/workflows/steps/checkout.yml b/.github/workflows/steps/checkout.yml
new file mode 100644
index 0000000..42d23b5
--- /dev/null
+++ b/.github/workflows/steps/checkout.yml
@@ -0,0 +1,4 @@
+- name: "Check out the repo"
+  uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+  with:
+    persist-credentials: false
diff --git a/.github/workflows/steps/install-dependencies.yml b/.github/workflows/steps/install-dependencies.yml
new file mode 100644
index 0000000..77b8255
--- /dev/null
+++ b/.github/workflows/steps/install-dependencies.yml
@@ -0,0 +1,3 @@
+- name: "Install dependencies"
+  run: |
+    python -m pip install -r requirements.pip
diff --git a/.github/workflows/steps/ruff.yml b/.github/workflows/steps/ruff.yml
new file mode 100644
index 0000000..fd0d36e
--- /dev/null
+++ b/.github/workflows/steps/ruff.yml
@@ -0,0 +1 @@
+- uses: astral-sh/ruff-action@eaf0ecdd668ceea36159ff9d91882c9795d89b49 # v3.4.0
diff --git a/.github/workflows/steps/setup-python.yml b/.github/workflows/steps/setup-python.yml
new file mode 100644
index 0000000..f98f779
--- /dev/null
+++ b/.github/workflows/steps/setup-python.yml
@@ -0,0 +1,2 @@
+- name: "Set up Python"
+  uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
diff --git a/AUTHORS.txt b/AUTHORS.txt
index 8762ecf..8890ad4 100644
--- a/AUTHORS.txt
+++ b/AUTHORS.txt
@@ -9,6 +9,7 @@ Daniel Murdin
 Doug Hellmann
 Hugh Perkins
 Jean-François Giraud
+Joshua Cannon
 Panayiotis Gavriil
 Petr Gladkiy
 Phil Kirkpatrick
diff --git a/cogapp/cogapp.py b/cogapp/cogapp.py
index 972e900..a6a1d34 100644
--- a/cogapp/cogapp.py
+++ b/cogapp/cogapp.py
@@ -7,6 +7,7 @@
 import io
 import linecache
 import os
+import os.path
 import re
 import shlex
 import sys
@@ -111,10 +112,11 @@ class CogCheckFailed(CogError):
 class CogGenerator(Redirectable):
     """A generator pulled from a source file."""
 
-    def __init__(self, options=None):
+    def __init__(self, filename, options=None):
         super().__init__()
         self.markers = []
         self.lines = []
+        self.filename = filename
         self.options = options or CogOptions()
 
     def parse_marker(self, line):
@@ -152,6 +154,7 @@ def evaluate(self, cog, globals, fname):
         cog.cogmodule.msg = self.msg
         cog.cogmodule.out = self.out
         cog.cogmodule.outl = self.outl
+        cog.cogmodule.include = self.include
         cog.cogmodule.error = self.error
 
         real_stdout = sys.stdout
@@ -205,6 +208,12 @@ def outl(self, sOut="", **kw):
         self.out(sOut, **kw)
         self.out("\n")
 
+    def include(self, filepath, **kw):
+        """The cog.include function."""
+        parent_dir = os.path.dirname(self.filename)
+        with open(os.path.join(parent_dir, filepath), "r") as f:
+            self.out(f.read(), **kw)
+
     def error(self, msg="Error raised by cog generator."):
         """The cog.error function.
 
@@ -466,7 +475,7 @@ def process_file(self, file_in, file_out, fname=None, globals=None):
                     file_out.write(line)
 
                 # `line` is the begin spec
-                gen = CogGenerator(options=self.options)
+                gen = CogGenerator(filename=file_name_in, options=self.options)
                 gen.set_output(stdout=self.stdout)
                 gen.parse_marker(line)
                 first_line_num = file_in.linenumber()
diff --git a/cogapp/test_cogapp.py b/cogapp/test_cogapp.py
index 9a394b7..913c01e 100644
--- a/cogapp/test_cogapp.py
+++ b/cogapp/test_cogapp.py
@@ -1449,6 +1449,60 @@ def test_change_dir(self):
         output = self.output.getvalue()
         self.assertIn("(changed)", output)
 
+    def test_cog_include(self):
+        d = {
+            "coglet": "World!",
+            "sub": {
+                "coglet": "Hello!",
+                "test.cog": """\
+                    //[[[cog
+                    cog.include("coglet")
+                    cog.include("./coglet")
+                    cog.include("../coglet")
+                    //]]]
+                    //[[[end]]]
+                    """,
+                "test.out": """\
+                    //[[[cog
+                    cog.include("coglet")
+                    cog.include("./coglet")
+                    cog.include("../coglet")
+                    //]]]
+                    Hello!
+                    Hello!
+                    World!
+                    //[[[end]]]
+                    """,
+            },
+        }
+
+        make_files(d)
+        self.cog.callable_main(["argv0", "-r", "sub/test.cog"])
+        self.assertFilesSame("sub/test.cog", "sub/test.out")
+        output = self.output.getvalue()
+        self.assertIn("(changed)", output)
+
+    def test_cog_include_with_stdin(self):
+        d = {"coglet": "Hello World!"}
+        make_files(d)
+        stdin = io.StringIO("--[[[cog cog.include('coglet') ]]]\n--[[[end]]]\n")
+
+        def restore_stdin(old_stdin):
+            sys.stdin = old_stdin
+
+        self.addCleanup(restore_stdin, sys.stdin)
+        sys.stdin = stdin
+
+        stderr = io.StringIO()
+        self.cog.set_output(stderr=stderr)
+        self.cog.callable_main(["argv0", "-"])
+        output = self.output.getvalue()
+        outerr = stderr.getvalue()
+        self.assertEqual(
+            output, "--[[[cog cog.include('coglet') ]]]\nHello World!\n--[[[end]]]\n"
+        )
+        self.assertEqual(outerr, "")
+
 
 class CogTestLineEndings(TestCaseWithTempDir):
     """Tests for -U option (force LF line-endings in output)."""
diff --git a/docs/module.rst b/docs/module.rst
index 6885058..702b173 100644
--- a/docs/module.rst
+++ b/docs/module.rst
@@ -25,6 +25,10 @@ The module contents are:
 **cog.outl**
     Same as **cog.out**, but adds a trailing newline.
 
+**cog.include(filepath=, **kwargs)**
+    Outputs the contents of the file at filepath (relative to the current file's directory).
+    (Keyword-arguments forwarded to **cog.out**)
+
 **cog.msg** `(msg)`
     Prints `msg` to stdout with a "Message: " prefix.