diff --git a/pw_build/py/pw_build/generate_python_package_gn.py b/pw_build/py/pw_build/generate_python_package_gn.py
new file mode 100755
index 0000000..b3681b6
--- /dev/null
+++ b/pw_build/py/pw_build/generate_python_package_gn.py
@@ -0,0 +1,115 @@
+#!/usr/bin/env python
+# Copyright 2020 The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+"""Generates a BUILD.gn for a Python package.
+
+Pass the script a list of paths to the root directory of a Python package (where
+setup.py is).
+
+Don't forget to add the pw_python_package to a top-level group, or it will not
+be included in the build.
+"""
+
+from datetime import datetime
+from pathlib import Path
+import sys
+from typing import Iterable, List, NamedTuple
+
+from pw_presubmit import git_repo
+
+_HEADER = f"""\
+# Copyright {datetime.now().year} The Pigweed Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may not
+# use this file except in compliance with the License. You may obtain a copy of
+# the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations under
+# the License.
+
+import("//build_overrides/pigweed.gni")
+
+import("$dir_pw_build/python.gni")
+"""
+
+
+class PackageFiles(NamedTuple):
+    setup: List[Path]
+    sources: List[Path]
+    tests: List[Path]
+    other: List[Path]
+
+
+def _find_package_files(root_dir: Path) -> PackageFiles:
+    files = git_repo.list_files(pathspecs=('*.py', '*.toml', '*.cfg'),
+                                repo_path=root_dir)
+
+    package_files = PackageFiles([], [], [], [])
+
+    for file in files:
+        if file.parent == root_dir:
+            if file.name == 'setup.py' or file.suffix != '.py':
+                package_files.setup.append(file)
+            elif file.stem.startswith('test_') or file.stem.endswith('_test'):
+                package_files.tests.append(file)
+            else:
+                package_files.other.append(file)
+        else:
+            package_files.sources.append(file)
+
+    return package_files
+
+
+def _gn_list(name: str, files: Iterable[Path], base: Path) -> Iterable[str]:
+    if files:
+        yield f'  {name} = ['
+        for file in files:
+            yield f'    "{file.relative_to(base).as_posix()}",'
+        yield '  ]'
+
+
+def generate_build_gn(root_dir: Path):
+    files = _find_package_files(root_dir)
+
+    yield _HEADER
+
+    yield 'pw_python_package("py") {'
+
+    yield from _gn_list('setup', files.setup, root_dir)
+    yield from _gn_list('sources', files.sources, root_dir)
+    yield from _gn_list('tests', files.tests, root_dir)
+
+    # Don't include the "other" files for now.
+    # yield from _gn_list('other', files.other, root_dir)
+
+    yield '}'
+
+
+def main(paths: Iterable[Path]):
+    for path in paths:
+        path.joinpath('BUILD.gn').write_text(
+            '\n'.join(generate_build_gn(path)) + '\n')
+
+
+if __name__ == '__main__':
+    if len(sys.argv) > 1:
+        main(Path(p).resolve() for p in sys.argv[1:])
+    else:
+        print(__file__, '', __doc__.strip(), sep='\n', file=sys.stderr)
+        sys.exit(1)