diff --git a/pyproject.toml b/pyproject.toml
index 240da5d7..11481040 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -28,7 +28,6 @@ classifiers = [
 requires-python = ">=3.8"
 dependencies = [
     "click",
-    "click-default-group",
     "importlib-resources>=5; python_version<'3.10'",
     "incremental",
     "jinja2",
@@ -146,9 +145,9 @@ strict = true
 exclude = '^src/towncrier/test/test_.*\.py$'
 
 [[tool.mypy.overrides]]
-module = 'click_default_group'
-# 2022-09-04: This library has no type annotations.
-ignore_missing_imports = true
+module = 'towncrier.click_default_group'
+# Vendored module without type annotations.
+ignore_errors = true
 
 [[tool.mypy.overrides]]
 module = 'incremental'
@@ -174,4 +173,5 @@ exclude_lines = [
 omit = [
     "src/towncrier/__main__.py",
     "src/towncrier/test/*",
+    "src/towncrier/click_default_group.py",
 ]
diff --git a/src/towncrier/_shell.py b/src/towncrier/_shell.py
index 0efe1b69..7aac1721 100644
--- a/src/towncrier/_shell.py
+++ b/src/towncrier/_shell.py
@@ -11,11 +11,10 @@
 
 import click
 
-from click_default_group import DefaultGroup
-
 from ._version import __version__
 from .build import _main as _build_cmd
 from .check import _main as _check_cmd
+from .click_default_group import DefaultGroup
 from .create import _main as _create_cmd
 
 
diff --git a/src/towncrier/click_default_group.py b/src/towncrier/click_default_group.py
new file mode 100644
index 00000000..6d5e69bd
--- /dev/null
+++ b/src/towncrier/click_default_group.py
@@ -0,0 +1,148 @@
+# SPDX-FileCopyrightText: 2015 Heungsub Lee <19982+sublee@users.noreply.github.com>
+#
+# SPDX-License-Identifier: BSD-3-Clause
+
+# Vendored from
+# https://github.com/click-contrib/click-default-group/tree/b671ae5325d186fe5ea7abb584f15852a1e931aa
+# Because the PyPI package could not be installed on modern Pips anymore and
+# the project looks unmaintaintained.
+
+"""
+   click_default_group
+   ~~~~~~~~~~~~~~~~~~~
+
+   Define a default subcommand by `default=True`:
+
+   .. sourcecode:: python
+
+      import click
+      from click_default_group import DefaultGroup
+
+      @click.group(cls=DefaultGroup, default_if_no_args=True)
+      def cli():
+          pass
+
+      @cli.command(default=True)
+      def foo():
+          click.echo('foo')
+
+      @cli.command()
+      def bar():
+          click.echo('bar')
+
+   Then you can invoke that without explicit subcommand name:
+
+   .. sourcecode:: console
+
+      $ cli.py --help
+      Usage: cli.py [OPTIONS] COMMAND [ARGS]...
+
+      Options:
+        --help    Show this message and exit.
+
+      Command:
+        foo*
+        bar
+
+      $ cli.py
+      foo
+      $ cli.py foo
+      foo
+      $ cli.py bar
+      bar
+
+"""
+import warnings
+
+import click
+
+
+__all__ = ["DefaultGroup"]
+__version__ = "1.2.2"
+
+
+class DefaultGroup(click.Group):
+    """Invokes a subcommand marked with `default=True` if any subcommand not
+    chosen.
+
+    :param default_if_no_args: resolves to the default command if no arguments
+                               passed.
+
+    """
+
+    def __init__(self, *args, **kwargs):
+        # To resolve as the default command.
+        if not kwargs.get("ignore_unknown_options", True):
+            raise ValueError("Default group accepts unknown options")
+        self.ignore_unknown_options = True
+        self.default_cmd_name = kwargs.pop("default", None)
+        self.default_if_no_args = kwargs.pop("default_if_no_args", False)
+        super().__init__(*args, **kwargs)
+
+    def set_default_command(self, command):
+        """Sets a command function as the default command."""
+        cmd_name = command.name
+        self.add_command(command)
+        self.default_cmd_name = cmd_name
+
+    def parse_args(self, ctx, args):
+        if not args and self.default_if_no_args:
+            args.insert(0, self.default_cmd_name)
+        return super().parse_args(ctx, args)
+
+    def get_command(self, ctx, cmd_name):
+        if cmd_name not in self.commands:
+            # No command name matched.
+            ctx.arg0 = cmd_name
+            cmd_name = self.default_cmd_name
+        return super().get_command(ctx, cmd_name)
+
+    def resolve_command(self, ctx, args):
+        base = super()
+        cmd_name, cmd, args = base.resolve_command(ctx, args)
+        if hasattr(ctx, "arg0"):
+            args.insert(0, ctx.arg0)
+            cmd_name = cmd.name
+        return cmd_name, cmd, args
+
+    def format_commands(self, ctx, formatter):
+        formatter = DefaultCommandFormatter(self, formatter, mark="*")
+        return super().format_commands(ctx, formatter)
+
+    def command(self, *args, **kwargs):
+        default = kwargs.pop("default", False)
+        decorator = super().command(*args, **kwargs)
+        if not default:
+            return decorator
+        warnings.warn(
+            "Use default param of DefaultGroup or " "set_default_command() instead",
+            DeprecationWarning,
+        )
+
+        def _decorator(f):
+            cmd = decorator(f)
+            self.set_default_command(cmd)
+            return cmd
+
+        return _decorator
+
+
+class DefaultCommandFormatter:
+    """Wraps a formatter to mark a default command."""
+
+    def __init__(self, group, formatter, mark="*"):
+        self.group = group
+        self.formatter = formatter
+        self.mark = mark
+
+    def __getattr__(self, attr):
+        return getattr(self.formatter, attr)
+
+    def write_dl(self, rows, *args, **kwargs):
+        rows_ = []
+        for cmd_name, help in rows:
+            if cmd_name == self.group.default_cmd_name:
+                rows_.insert(0, (cmd_name + self.mark, help))
+            else:
+                rows_.append((cmd_name, help))
+        return self.formatter.write_dl(rows_, *args, **kwargs)
diff --git a/src/towncrier/newsfragments/540.bugfix b/src/towncrier/newsfragments/540.bugfix
new file mode 100644
index 00000000..7e2f12b0
--- /dev/null
+++ b/src/towncrier/newsfragments/540.bugfix
@@ -0,0 +1 @@
+Towncrier now vendors the click-default-group package that prevented installations on modern Pips.