diff --git a/CHANGES b/CHANGES
index b7eff7554..c253055bd 100644
--- a/CHANGES
+++ b/CHANGES
@@ -12,8 +12,12 @@ Incompatible changes
 Deprecated
 ----------
 
+* The ``template_dir`` argument of ``sphinx.ext.autosummary.generate.
+  AutosummaryRenderer``
 * The ``module`` argument of ``sphinx.ext.autosummary.generate.
   find_autosummary_in_docstring()``
+* The ``template_dir`` argument of ``sphinx.ext.autosummary.generate.
+  generate_autosummary_docs()``
 
 Features added
 --------------
diff --git a/doc/extdev/deprecated.rst b/doc/extdev/deprecated.rst
index b0468a39f..a62dee560 100644
--- a/doc/extdev/deprecated.rst
+++ b/doc/extdev/deprecated.rst
@@ -26,12 +26,24 @@ The following is a list of deprecated interfaces.
      - (will be) Removed
      - Alternatives
 
+   * - The ``template_dir`` argument of
+       ``sphinx.ext.autosummary.generate.AutosummaryRenderer``
+     - 3.1
+     - 5.0
+     - N/A
+
    * - The ``module`` argument of
        ``sphinx.ext.autosummary.generate.find_autosummary_in_docstring()``
      - 3.0
      - 5.0
      - N/A
 
+   * - The ``template_dir`` argument of
+       ``sphinx.ext.autosummary.generate.generate_autosummary_docs()``
+     - 3.1
+     - 5.0
+     - N/A
+
    * - ``desc_signature['first']``
      -
      - 3.0
diff --git a/sphinx/ext/autosummary/generate.py b/sphinx/ext/autosummary/generate.py
index 4d680acd6..8a056f55f 100644
--- a/sphinx/ext/autosummary/generate.py
+++ b/sphinx/ext/autosummary/generate.py
@@ -127,7 +127,11 @@ def _underline(title: str, line: str = '=') -> str:
 class AutosummaryRenderer:
     """A helper class for rendering."""
 
-    def __init__(self, builder: Builder, template_dir: str) -> None:
+    def __init__(self, builder: Builder, template_dir: str = None) -> None:
+        if template_dir:
+            warnings.warn('template_dir argument for AutosummaryRenderer is deprecated.',
+                          RemovedInSphinx50Warning)
+
         system_templates_path = [os.path.join(package_dir, 'ext', 'autosummary', 'templates')]
         loader = SphinxTemplateLoader(builder.srcdir,
                                       builder.config.templates_path,
@@ -277,6 +281,10 @@ def generate_autosummary_docs(sources: List[str], output_dir: str = None,
     else:
         _warn = logger.warning
 
+    if template_dir:
+        warnings.warn('template_dir argument for generate_autosummary_docs() is deprecated.',
+                      RemovedInSphinx50Warning)
+
     showed_sources = list(sorted(sources))
     if len(showed_sources) > 20:
         showed_sources = showed_sources[:10] + ['...'] + showed_sources[-10:]
@@ -289,7 +297,7 @@ def generate_autosummary_docs(sources: List[str], output_dir: str = None,
     if base_path is not None:
         sources = [os.path.join(base_path, filename) for filename in sources]
 
-    template = AutosummaryRenderer(builder, template_dir)
+    template = AutosummaryRenderer(builder)
 
     # read
     items = find_autosummary_in_files(sources)
@@ -337,7 +345,6 @@ def generate_autosummary_docs(sources: List[str], output_dir: str = None,
         generate_autosummary_docs(new_files, output_dir=output_dir,
                                   suffix=suffix, warn=warn, info=info,
                                   base_path=base_path, builder=builder,
-                                  template_dir=template_dir,
                                   imported_members=imported_members, app=app,
                                   overwrite=overwrite)