diff --git a/.github/workflows/cygwin.yml b/.github/workflows/cygwin.yml
new file mode 100644
index 000000000000..7b5096ef3e19
--- /dev/null
+++ b/.github/workflows/cygwin.yml
@@ -0,0 +1,251 @@
+---
+name: Cygwin Tests
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.number }}-${{ github.event.ref }}
+  cancel-in-progress: true
+
+on:
+  push:
+    branches:
+      - main
+      - v[0-9]+.[0-9]+.[0-9x]+
+    tags:
+      - v*
+    paths:
+      - 'src/**'
+      - '.github/workflows/cygwin.yml'
+  pull_request:
+    types:
+      - opened
+      - synchronize
+      - reopened
+      - labeled
+    branches-ignore:
+      - v[0-9]+.[0-9]+.[0-9x]+-doc
+    paths:
+      - 'src/**'
+      - '.github/workflows/cygwin.yml'
+  schedule:
+    # 5:47 UTC on Saturdays
+    - cron: "47 5 * * 6"
+  workflow_dispatch:
+    workflow: "*"
+
+permissions:
+  contents: read
+
+env:
+  NO_AT_BRIDGE: 1  # Necessary for GTK3 interactive test.
+  OPENBLAS_NUM_THREADS: 1
+  PYTHONFAULTHANDLER: 1
+  SHELLOPTS: igncr
+  CYGWIN_NOWINPATH: 1
+  CHERE_INVOKING: 1
+  TMP: /tmp
+  TEMP: /tmp
+
+jobs:
+
+  test-cygwin:
+    runs-on: windows-latest
+    name: Python 3.${{ matrix.python-minor-version }} on Cygwin
+    if: |
+      github.event_name == 'workflow_dispatch' ||
+      (
+        github.repository == 'matplotlib/matplotlib' &&
+        !contains(github.event.head_commit.message, '[ci skip]') &&
+        !contains(github.event.head_commit.message, '[skip ci]') &&
+        !contains(github.event.head_commit.message, '[skip github]') &&
+        (
+          github.event_name == 'push' ||
+          github.event_name == 'pull_request' &&
+          (
+            (
+              github.event.action == 'labeled' &&
+              github.event.label.name == 'Run cygwin'
+            ) ||
+            contains(github.event.pull_request.labels.*.name, 'Run cygwin')
+          )
+        )
+      )
+    strategy:
+      matrix:
+        python-minor-version: [8, 9]
+
+    steps:
+      - name: Fix line endings
+        run: git config --global core.autocrlf input
+
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+
+      - uses: cygwin/cygwin-install-action@v2
+        with:
+          packages: >-
+            ccache gcc-g++ gdb git graphviz libcairo-devel libffi-devel
+            libgeos-devel libQt5Core-devel pkgconf libglib2.0-devel
+            noto-cjk-fonts
+            python3${{ matrix.python-minor-version }}-devel
+            python3${{ matrix.python-minor-version }}-pip
+            python3${{ matrix.python-minor-version }}-wheel
+            python3${{ matrix.python-minor-version }}-setuptools
+            python3${{ matrix.python-minor-version }}-cycler
+            python3${{ matrix.python-minor-version }}-dateutil
+            python3${{ matrix.python-minor-version }}-fonttools
+            python3${{ matrix.python-minor-version }}-imaging
+            python3${{ matrix.python-minor-version }}-kiwisolver
+            python3${{ matrix.python-minor-version }}-numpy
+            python3${{ matrix.python-minor-version }}-packaging
+            python3${{ matrix.python-minor-version }}-pyparsing
+            python3${{ matrix.python-minor-version }}-sip
+            python3${{ matrix.python-minor-version }}-sphinx
+            python-cairo-devel
+            python3${{ matrix.python-minor-version }}-cairo
+            python3${{ matrix.python-minor-version }}-gi
+            python3${{ matrix.python-minor-version }}-matplotlib
+            xorg-server-extra libxcb-icccm4 libxcb-image0
+            libxcb-keysyms1 libxcb-randr0 libxcb-render-util0
+            libxcb-xinerama0
+            make autoconf autoconf2.5 automake automake1.10 libtool m4
+            libqhull-devel libfreetype-devel
+            libjpeg-devel libwebp-devel
+
+      - name: Set runner username to root and id to 0
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        # GitHub Actions runs everything as Administrator.  I don't
+        # know how to test for this, so set the uid for the CI job so
+        # that the existing unix root detection will work.
+        run: |
+           /bin/mkpasswd.exe -c | sed -e "s/$(id -u)/0/" >/etc/passwd
+
+      - name: Mark test repo safe
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          git.exe config --global --add safe.directory /proc/cygdrive/d/a/matplotlib/matplotlib
+          git config --global --add safe.directory /cygdrive/d/a/matplotlib/matplotlib
+          C:/cygwin/bin/git.exe config --global --add safe.directory D:/a/matplotlib/matplotlib
+          /usr/bin/git config --global --add safe.directory /cygdrive/d/a/matplotlib/matplotlib
+
+      - name: Use dash for /bin/sh
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          ls -l /bin/sh.exe /bin/bash.exe /bin/dash.exe
+          /bin/rm -f /bin/sh.exe || exit 1
+          cp -sf /bin/dash.exe /bin/sh.exe || exit 1
+          ls -l /bin/sh.exe /bin/bash.exe /bin/dash.exe
+        # FreeType build fails with bash, succeeds with dash
+
+      - name: Cache pip
+        uses: actions/cache@v3
+        with:
+          path: C:\cygwin\home\runneradmin\.cache\pip
+          key: Cygwin-py3.${{ matrix.python-minor-version }}-pip-${{ hashFiles('requirements/*/*.txt') }}
+          restore-keys: |
+            ${{ matrix.os }}-py3.${{ matrix.python-minor-version }}-pip-
+
+      - name: Cache ccache
+        uses: actions/cache@v3
+        with:
+          path: C:\cygwin\home\runneradmin\.ccache
+          key: Cygwin-py3.${{ matrix.python-minor-version }}-ccache-${{ hashFiles('src/*') }}
+          restore-keys: Cygwin-py3.${{ matrix.python-minor-version }}-ccache-
+
+      - name: Cache Matplotlib
+        uses: actions/cache@v3
+        with:
+          path: |
+            C:\cygwin\home\runneradmin\.cache\matplotlib
+            !C:\cygwin\home\runneradmin\.cache\matplotlib\tex.cache
+            !C:\cygwin\home\runneradmin\.cache\matplotlib\test_cache
+          key: 1-Cygwin-py3.${{ matrix.python-minor-version }}-mpl-${{ github.ref }}-${{ github.sha }}
+          restore-keys: |
+            1-Cygwin-py3.${{ matrix.python-minor-version }}-mpl-${{ github.ref }}-
+            1-Cygwin-py3.${{ matrix.python-minor-version }}-mpl-
+
+      - name: Ensure correct Python version
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          /usr/sbin/alternatives --set python /usr/bin/python3.${{ matrix.python-minor-version }}
+          /usr/sbin/alternatives --set python3 /usr/bin/python3.${{ matrix.python-minor-version }}
+
+      - name: Install Python dependencies
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          python -m pip install --upgrade pip 'setuptools<60' wheel
+          python -m pip install kiwisolver 'numpy!=1.21.*' pillow importlib_resources
+          grep -v -F -e psutil requirements/testing/all.txt >requirements_test.txt
+          python -m pip install --upgrade 'contourpy>=1.0.1' cycler fonttools \
+              packaging pyparsing python-dateutil setuptools-scm \
+              -r requirements_test.txt sphinx ipython
+          python -m pip install --upgrade pycairo 'cairocffi>=0.8' PyGObject &&
+             python -c 'import gi; gi.require_version("Gtk", "3.0"); from gi.repository import Gtk' &&
+             echo 'PyGObject is available' ||
+             echo 'PyGObject is not available'
+          python -m pip install --upgrade pyqt5  &&
+             python -c 'import PyQt5.QtCore' &&
+             echo 'PyQt5 is available' ||
+             echo 'PyQt5 is not available'
+          python -mpip install --upgrade pyside2 &&
+              python -c 'import PySide2.QtCore' &&
+              echo 'PySide2 is available' ||
+              echo 'PySide2 is not available'
+          python -m pip uninstall --yes wxpython || echo 'wxPython already uninstalled'
+
+      - name: Install Matplotlib
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        env:
+          AUTOCONF: /usr/bin/autoconf-2.69
+          MAKEFLAGS: dw
+        run: |
+          ccache -s
+          git describe
+          cat <<EOT >> mplsetup.cfg
+          [rc_options]
+          backend=Agg
+
+          [libs]
+          system_freetype = False
+          system_qhull = True
+          EOT
+          cat mplsetup.cfg
+          # All dependencies must have been pre-installed, so that the minver
+          # constraints are held.
+          python -m pip install --no-deps -ve .
+
+      - name: Find DLLs to rebase
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          find {/usr,/usr/local}/{bin,lib/python3.*/site-packages} /usr/lib/lapack . -name \*.exe -o -name \*.dll -print >files_to_rebase.txt
+
+      - name: Rebase DLL list
+        shell: ash.exe "{0}"
+        run: "rebase --database --filelist=files_to_rebase.txt"
+        # Inplace modification of DLLs to assign non-overlapping load
+        # addresses so fork() works as expected.  Ash is used as it
+        # does not link against any Cygwin DLLs that might need to be
+        # rebased.
+
+      - name: Check that Matplotlib imports
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          /usr/bin/python -c "import matplotlib as mpl; import matplotlib.pyplot as plt"
+
+      - name: Set ffmpeg path
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        run: |
+          oldmplrc=$(python -c "from matplotlib import matplotlib_fname as mplrc_file; print(mplrc_file())")
+          echo "${oldmplrc}"
+          mkdir -p ~/.matplotlib/
+          sed -E -e 's~#animation\.ffmpeg_path:.+~animation.ffmpeg_path: /usr/bin/ffmpeg.exe~' "${oldmplrc}" >~/.matplotlib/matplotlibrc
+
+      - name: Run pytest
+        shell: bash.exe -eo pipefail -o igncr "{0}"
+        id: cygwin-run-pytest
+        run: |
+          xvfb-run python -mpytest -raR -n auto \
+            --maxfail=50 --timeout=300 --durations=25 \
+            --cov-report=xml --cov=lib --log-level=DEBUG --color=yes
+
+      - name: Upload code coverage
+        uses: codecov/codecov-action@v3
diff --git a/lib/matplotlib/testing/__init__.py b/lib/matplotlib/testing/__init__.py
index 6f54a4866c18..2df6814efa64 100644
--- a/lib/matplotlib/testing/__init__.py
+++ b/lib/matplotlib/testing/__init__.py
@@ -50,6 +50,69 @@ def setup():
     set_reproducibility_for_testing()
 
 
+def subprocess_run_for_testing(
+        command: "list[str]",
+        env: "dict[str, str]" = None,
+        timeout: float = None,
+        stdout=None,
+        stderr=None,
+        check: bool = False,
+        text: bool = True,
+        capture_output: bool = False
+) -> "subprocess.Popen":
+    """
+    Create and run a subprocess.
+
+    Thin wrapper around `subprocess.run`, intended for testing.  Will
+    mark fork() failures on Cygwin as expected failures: not a
+    success, but not indicating a problem with the code either.
+
+    Parameters
+    ----------
+    args : list of str
+    env : dict[str, str]
+    timeout : float
+    stdout, stderr
+    check : bool
+    text : bool
+        Also called ``universal_newlines`` in subprocess.  I chose this
+        name since the main effect is returning bytes (`False`) vs. str
+        (`True`), though it also tries to normalize newlines across
+        platforms.
+    capture_output : bool
+        Set stdout and stderr to subprocess.PIPE
+
+    Returns
+    -------
+    proc : subprocess.Popen
+
+    See Also
+    --------
+    subprocess.run
+
+    Raises
+    ------
+    pytest.xfail
+        If platform is Cygwin and subprocess reports a fork() failure.
+    """
+    if capture_output:
+        stdout = stderr = subprocess.PIPE
+    try:
+        proc = subprocess.run(
+            command, env=env,
+            timeout=timeout, check=check,
+            stdout=stdout, stderr=stderr,
+            text=text
+        )
+    except BlockingIOError:
+        if sys.platform == "cygwin":
+            # Might want to make this more specific
+            import pytest
+            pytest.xfail("Fork failure")
+        raise
+    return proc
+
+
 def subprocess_run_helper(func, *args, timeout, extra_env=None):
     """
     Run a function in a sub-process.
@@ -66,16 +129,19 @@ def subprocess_run_helper(func, *args, timeout, extra_env=None):
     """
     target = func.__name__
     module = func.__module__
-    proc = subprocess.run(
-        [sys.executable,
-         "-c",
-         f"from {module} import {target}; {target}()",
-         *args],
+    proc = subprocess_run_for_testing(
+        [
+            sys.executable,
+            "-c",
+            f"from {module} import {target}; {target}()",
+            *args
+        ],
         env={**os.environ, "SOURCE_DATE_EPOCH": "0", **(extra_env or {})},
         timeout=timeout, check=True,
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
-        universal_newlines=True)
+        text=True
+    )
     return proc
 
 
diff --git a/lib/matplotlib/tests/test_preprocess_data.py b/lib/matplotlib/tests/test_preprocess_data.py
index a95a72e7f78d..693385ee5b40 100644
--- a/lib/matplotlib/tests/test_preprocess_data.py
+++ b/lib/matplotlib/tests/test_preprocess_data.py
@@ -1,5 +1,4 @@
 import re
-import subprocess
 import sys
 
 import numpy as np
@@ -7,6 +6,7 @@
 
 from matplotlib import _preprocess_data
 from matplotlib.axes import Axes
+from matplotlib.testing import subprocess_run_for_testing
 from matplotlib.testing.decorators import check_figures_equal
 
 # Notes on testing the plotting functions itself
@@ -259,7 +259,9 @@ def test_data_parameter_replacement():
         "import matplotlib.pyplot as plt"
     )
     cmd = [sys.executable, "-c", program]
-    completed_proc = subprocess.run(cmd, text=True, capture_output=True)
+    completed_proc = subprocess_run_for_testing(
+        cmd, text=True, capture_output=True
+    )
     assert 'data parameter docstring error' not in completed_proc.stderr
 
 
diff --git a/lib/matplotlib/tests/test_pyplot.py b/lib/matplotlib/tests/test_pyplot.py
index 95e3174d8ae8..292f81f1292e 100644
--- a/lib/matplotlib/tests/test_pyplot.py
+++ b/lib/matplotlib/tests/test_pyplot.py
@@ -1,13 +1,13 @@
 import difflib
 
 import numpy as np
-import subprocess
 import sys
 from pathlib import Path
 
 import pytest
 
 import matplotlib as mpl
+from matplotlib.testing import subprocess_run_for_testing
 from matplotlib import pyplot as plt
 from matplotlib._api import MatplotlibDeprecationWarning
 
@@ -20,8 +20,9 @@ def test_pyplot_up_to_date(tmpdir):
     plt_file = tmpdir.join('pyplot.py')
     plt_file.write_text(orig_contents, 'utf-8')
 
-    subprocess.run([sys.executable, str(gen_script), str(plt_file)],
-                   check=True)
+    subprocess_run_for_testing(
+        [sys.executable, str(gen_script), str(plt_file)],
+        check=True)
     new_contents = plt_file.read_text('utf-8')
 
     if orig_contents != new_contents:
diff --git a/lib/matplotlib/tests/test_sphinxext.py b/lib/matplotlib/tests/test_sphinxext.py
index 41575d3a3ce1..669723be1d55 100644
--- a/lib/matplotlib/tests/test_sphinxext.py
+++ b/lib/matplotlib/tests/test_sphinxext.py
@@ -4,9 +4,9 @@
 import os
 from pathlib import Path
 import shutil
-from subprocess import Popen, PIPE
 import sys
 
+from matplotlib.testing import subprocess_run_for_testing
 import pytest
 
 
@@ -19,9 +19,11 @@ def build_sphinx_html(source_dir, doctree_dir, html_dir, extra_args=None):
     extra_args = [] if extra_args is None else extra_args
     cmd = [sys.executable, '-msphinx', '-W', '-b', 'html',
            '-d', str(doctree_dir), str(source_dir), str(html_dir), *extra_args]
-    proc = Popen(cmd, stdout=PIPE, stderr=PIPE, universal_newlines=True,
-                 env={**os.environ, "MPLBACKEND": ""})
-    out, err = proc.communicate()
+    proc = subprocess_run_for_testing(
+        cmd, capture_output=True, text=True,
+        env={**os.environ, "MPLBACKEND": ""})
+    out = proc.stdout
+    err = proc.stderr
 
     assert proc.returncode == 0, \
         f"sphinx build failed with stdout:\n{out}\nstderr:\n{err}\n"
@@ -44,10 +46,12 @@ def test_tinypages(tmp_path):
     # On CI, gcov emits warnings (due to agg headers being included with the
     # same name in multiple extension modules -- but we don't care about their
     # coverage anyways); hide them using GCOV_ERROR_FILE.
-    proc = Popen(
-        cmd, stdout=PIPE, stderr=PIPE, universal_newlines=True,
-        env={**os.environ, "MPLBACKEND": "", "GCOV_ERROR_FILE": os.devnull})
-    out, err = proc.communicate()
+    proc = subprocess_run_for_testing(
+        cmd, capture_output=True, text=True,
+        env={**os.environ, "MPLBACKEND": "", "GCOV_ERROR_FILE": os.devnull}
+    )
+    out = proc.stdout
+    err = proc.stderr
 
     # Build the pages with warnings turned into errors
     build_sphinx_html(tmp_path, doctree_dir, html_dir)
diff --git a/src/mplutils.h b/src/mplutils.h
index 39d98ed02e8f..2eb9e2f563f3 100644
--- a/src/mplutils.h
+++ b/src/mplutils.h
@@ -6,6 +6,7 @@
 #define MPLUTILS_H
 #define PY_SSIZE_T_CLEAN
 
+#include <Python.h>
 #include <stdint.h>
 
 #ifdef _POSIX_C_SOURCE
@@ -27,7 +28,6 @@
 #endif
 #endif
 
-#include <Python.h>
 
 inline double mpl_round(double v)
 {