diff --git a/doc/api/api_changes_3.3/deprecations.rst b/doc/api/api_changes_3.3/deprecations.rst
index 5635c5f73c86..06b454a44a0a 100644
--- a/doc/api/api_changes_3.3/deprecations.rst
+++ b/doc/api/api_changes_3.3/deprecations.rst
@@ -554,3 +554,7 @@ in which they are given.  This only affects the interaction between the
 properties: the *color* property now needs to be passed first in order not to
 override the other properties.  This is consistent with e.g. `.Artist.update`,
 which did not reorder the properties passed to it.
+
+Passing multiple keys as a single comma-separated string or multiple arguments to `.ToolManager.update_keymap`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This is deprecated; pass keys as a list of strings instead.
diff --git a/lib/matplotlib/backend_managers.py b/lib/matplotlib/backend_managers.py
index 375182d2efdf..c59c3c65ec06 100644
--- a/lib/matplotlib/backend_managers.py
+++ b/lib/matplotlib/backend_managers.py
@@ -183,7 +183,8 @@ def _remove_keys(self, name):
         for k in self.get_tool_keymap(name):
             del self._keys[k]
 
-    def update_keymap(self, name, *keys):
+    @cbook._delete_parameter("3.3", "args")
+    def update_keymap(self, name, key, *args):
         """
         Set the keymap to associate with the specified tool.
 
@@ -191,17 +192,23 @@ def update_keymap(self, name, *keys):
         ----------
         name : str
             Name of the Tool.
-        keys : list of str
+        keys : str or list of str
             Keys to associate with the tool.
         """
-
         if name not in self._tools:
             raise KeyError('%s not in Tools' % name)
-
         self._remove_keys(name)
-
-        for key in keys:
-            for k in validate_stringlist(key):
+        for key in [key, *args]:
+            if isinstance(key, str) and validate_stringlist(key) != [key]:
+                cbook.warn_deprecated(
+                    "3.3", message="Passing a list of keys as a single "
+                    "comma-separated string is deprecated since %(since)s and "
+                    "support will be removed %(removal)s; pass keys as a list "
+                    "of strings instead.")
+                key = validate_stringlist(key)
+            if isinstance(key, str):
+                key = [key]
+            for k in key:
                 if k in self._keys:
                     cbook._warn_external('Key %s changed from %s to %s' %
                                          (k, self._keys[k], name))