diff --git a/CHANGES b/CHANGES
index 8fa9f5707..b95582e2c 100644
--- a/CHANGES
+++ b/CHANGES
@@ -23,6 +23,7 @@ Deprecated
 * ``sphinx.ext.autodoc.SlotsAttributeDocumenter``
 * ``sphinx.ext.autodoc.TypeVarDocumenter``
 * ``sphinx.ext.autodoc.importer._getannotations()``
+* ``sphinx.ext.autodoc.importer._getmro()``
 * ``sphinx.pycode.ModuleAnalyzer.parse()``
 * ``sphinx.util.osutil.movefile()``
 * ``sphinx.util.requests.is_ssl_error()``
diff --git a/doc/extdev/deprecated.rst b/doc/extdev/deprecated.rst
index c167e509c..30d108035 100644
--- a/doc/extdev/deprecated.rst
+++ b/doc/extdev/deprecated.rst
@@ -72,6 +72,11 @@ The following is a list of deprecated interfaces.
      - 4.0
      - ``sphinx.util.inspect.getannotations()``
 
+   * - ``sphinx.ext.autodoc.importer._getmro()``
+     - 3.4
+     - 4.0
+     - ``sphinx.util.inspect.getmro()``
+
    * - ``sphinx.pycode.ModuleAnalyzer.parse()``
      - 3.4
      - 5.0
diff --git a/sphinx/ext/autodoc/importer.py b/sphinx/ext/autodoc/importer.py
index cb97e0c72..ec05a8a3d 100644
--- a/sphinx/ext/autodoc/importer.py
+++ b/sphinx/ext/autodoc/importer.py
@@ -16,7 +16,8 @@ from typing import Any, Callable, Dict, List, Mapping, NamedTuple, Optional, Tup
 from sphinx.deprecation import RemovedInSphinx40Warning, deprecated_alias
 from sphinx.pycode import ModuleAnalyzer
 from sphinx.util import logging
-from sphinx.util.inspect import getannotations, getslots, isclass, isenumclass, safe_getattr
+from sphinx.util.inspect import (getannotations, getmro, getslots, isclass, isenumclass,
+                                 safe_getattr)
 
 if False:
     # For type annotation
@@ -165,12 +166,9 @@ Attribute = NamedTuple('Attribute', [('name', str),
 
 
 def _getmro(obj: Any) -> Tuple["Type", ...]:
-    """Get __mro__ from given *obj* safely."""
-    __mro__ = safe_getattr(obj, '__mro__', None)
-    if isinstance(__mro__, tuple):
-        return __mro__
-    else:
-        return tuple()
+    warnings.warn('sphinx.ext.autodoc.importer._getmro() is deprecated.',
+                  RemovedInSphinx40Warning)
+    return getmro(obj)
 
 
 def _getannotations(obj: Any) -> Mapping[str, Any]:
@@ -224,7 +222,7 @@ def get_object_members(subject: Any, objpath: List[str], attrgetter: Callable,
             continue
 
     # annotation only member (ex. attr: int)
-    for i, cls in enumerate(_getmro(subject)):
+    for i, cls in enumerate(getmro(subject)):
         try:
             for name in getannotations(cls):
                 name = unmangle(cls, name)
diff --git a/sphinx/util/inspect.py b/sphinx/util/inspect.py
index df469a5ae..a26c818c0 100644
--- a/sphinx/util/inspect.py
+++ b/sphinx/util/inspect.py
@@ -36,6 +36,10 @@ else:
     MethodDescriptorType = type(str.join)
     WrapperDescriptorType = type(dict.__dict__['fromkeys'])
 
+if False:
+    # For type annotation
+    from typing import Type  # NOQA
+
 logger = logging.getLogger(__name__)
 
 memory_address_re = re.compile(r' at 0x[0-9a-f]{8,16}(?=>)', re.IGNORECASE)
@@ -166,6 +170,18 @@ def getannotations(obj: Any) -> Mapping[str, Any]:
         return {}
 
 
+def getmro(obj: Any) -> Tuple["Type", ...]:
+    """Get __mro__ from given *obj* safely.
+
+    Raises AttributeError if given *obj* raises an error on accessing __mro__.
+    """
+    __mro__ = safe_getattr(obj, '__mro__', None)
+    if isinstance(__mro__, tuple):
+        return __mro__
+    else:
+        return tuple()
+
+
 def getslots(obj: Any) -> Optional[Dict]:
     """Get __slots__ attribute of the class as dict.