diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index d537598ac16433..bab99e75c93282 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1234,6 +1234,7 @@ def set_data(self, path, data, *, _mode=0o666):
             parent, part = _path_split(parent)
             path_parts.append(part)
         # Create needed directories.
+        just_created_cache_dir = False
         for part in reversed(path_parts):
             parent = _path_join(parent, part)
             try:
@@ -1247,6 +1248,11 @@ def set_data(self, path, data, *, _mode=0o666):
                 _bootstrap._verbose_message('could not create {!r}: {!r}',
                                             parent, exc)
                 return
+            else:
+                just_created_cache_dir = True
+        # To avoid polluting backups with __pycache__ directories and .pyc files
+        if just_created_cache_dir:
+            _exclude_directory_from_backups(parent)
         try:
             _write_atomic(path, data, _mode)
             _bootstrap._verbose_message('created {!r}', path)
@@ -1256,6 +1262,21 @@ def set_data(self, path, data, *, _mode=0o666):
                                         exc)
 
 
+def _exclude_directory_from_backups(directory):
+    """Exclude the directory from backups using a CACHEDIR.TAG file.
+
+    If the file exists or there's a permission error this is a no-op.
+    """
+    try:
+        with _io.FileIO(_path_join(directory, 'CACHEDIR.TAG'), 'x') as f:
+            f.write(b"""Signature: 8a477f597d28d172789f06886806bc55
+# This file is a cache directory tag created by CPython.
+# For information about cache directory tags, see: https://bford.info/cachedir/
+""")
+    except (FileExistsError, PermissionError):
+        pass
+
+
 class SourcelessFileLoader(FileLoader, _LoaderBasics):
 
     """Loader which handles sourceless file imports."""
diff --git a/Lib/test/test_import/__init__.py b/Lib/test/test_import/__init__.py
index 48c0a43f29e27f..6b4f314bf4e955 100644
--- a/Lib/test/test_import/__init__.py
+++ b/Lib/test/test_import/__init__.py
@@ -1144,6 +1144,21 @@ def test_import_pyc_path(self):
                         'bytecode file {!r} for {!r} does not '
                         'exist'.format(pyc_path, TESTFN))
 
+    @skip_if_dont_write_bytecode
+    def test_cachedir_tag_exists(self):
+        self.assertFalse(os.path.exists('__pycache__'))
+        __import__(TESTFN)
+        self.assertTrue(os.path.exists('__pycache__'))
+        cachedir_tag = os.path.join('__pycache__', 'CACHEDIR.TAG')
+        self.assertTrue(os.path.exists(cachedir_tag),
+                        f'CACHEDIR.TAG file {cachedir_tag} for {TESTFN} does not exist')
+        with open(cachedir_tag) as f:
+            cachedir_tag_content = f.read()
+        self.assertTrue(
+            cachedir_tag_content.startswith('Signature: 8a477f597d28d172789f06886806bc55'),
+            f'CACHEDIR.TAG file {cachedir_tag} for {TESTFN} does not contain the right signature',
+        )
+
     @unittest.skipUnless(os.name == 'posix',
                          "test meaningful only on posix systems")
     @skip_if_dont_write_bytecode