@@ -71,10 +71,33 @@ def _gen_cmap_d():
     return cmap_d
 
 
+class _DeprecatedCmapDict(dict):
+    def __getitem__(self, key):
+        self._warn_deprecated()
+        return dict.__getitem__(self, key)
+
+    def __setitem__(self, key, val):
+        self._warn_deprecated()
+        dict.__setitem__(self, key, val)
+
+    def get(self, key, default=None):
+        self._warn_deprecated()
+        return dict.get(self, key, default)
+
+    def _warn_deprecated(self):
+        cbook.warn_deprecated(
+            "3.3",
+            message="The global colormaps dictionary is no longer "
+                    "considered public API.",
+            alternative="Please use register_cmap() and get_cmap() to "
+                        "access the contents of the dictionary."
+        )
+
+
 _cmap_d = _gen_cmap_d()
 locals().update(_cmap_d)
 # This is no longer considered public API
-cmap_d = _cmap_d
+cmap_d = _DeprecatedCmapDict(_cmap_d)
 
 
 # Continue with definitions ...
 
@@ -126,6 +126,17 @@ def test_colormap_global_set_warn():
     plt.register_cmap(cmap=orig_cmap)
 
 
+def test_colormap_dict_deprecate():
+    # Make sure we warn on get and set access into cmap_d
+    with pytest.warns(cbook.MatplotlibDeprecationWarning,
+                      match="The global colormaps dictionary is no longer"):
+        cm = plt.cm.cmap_d['viridis']
+
+    with pytest.warns(cbook.MatplotlibDeprecationWarning,
+                      match="The global colormaps dictionary is no longer"):
+        plt.cm.cmap_d['test'] = cm
+
+
 def test_colormap_copy():
     cm = plt.cm.Reds
     cm_copy = copy.copy(cm)