diff --git a/doc/api/next_api_changes/deprecations/20753-AL.rst b/doc/api/next_api_changes/deprecations/20753-AL.rst
new file mode 100644
index 000000000000..75b989f5c658
--- /dev/null
+++ b/doc/api/next_api_changes/deprecations/20753-AL.rst
@@ -0,0 +1,4 @@
+Case-insensitive scales
+~~~~~~~~~~~~~~~~~~~~~~~
+Previously, scales could be set case-insensitively (e.g. ``set_xscale("LoG")``).
+This is deprecated; all builtin scales use lowercase names.
diff --git a/lib/matplotlib/scale.py b/lib/matplotlib/scale.py
index 62dc5192a30d..180906106747 100644
--- a/lib/matplotlib/scale.py
+++ b/lib/matplotlib/scale.py
@@ -588,9 +588,13 @@ def scale_factory(scale, axis, **kwargs):
     scale : {%(names)s}
     axis : `matplotlib.axis.Axis`
     """
-    scale = scale.lower()
-    _api.check_in_list(_scale_mapping, scale=scale)
-    return _scale_mapping[scale](axis, **kwargs)
+    if scale != scale.lower():
+        _api.warn_deprecated(
+            "3.5", message="Support for case-insensitive scales is deprecated "
+            "since %(since)s and support will be removed %(removal)s.")
+        scale = scale.lower()
+    scale_cls = _api.check_getitem(_scale_mapping, scale=scale)
+    return scale_cls(axis, **kwargs)
 
 
 if scale_factory.__doc__: