matplotlib
diff --git a/‎doc/users/next_whats_new/2019-08_tac.rst
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diff --git a/‎lib/matplotlib/cm.py
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diff --git a/‎lib/matplotlib/tests/test_cm.py
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@@ -0,0 +1,6 @@
+
+Add ``cm.deregister_cmap`` function
+-----------------------------------
+
+`.cm.deregister_cmap` allows users to remove a color map that they
+have previously registered.
@@ -144,6 +144,28 @@ def get_cmap(name=None, lut=None):
         return cmap_d[name]._resample(lut)
 
 
+def deregister_cmap(name):
+    """
+    Remove a colormap recognized by :func:`get_cmap`.
+
+    You may not remove built in color maps.
+
+    If the named color map is not registered, returns with no error, raises
+    if you try to de-register a default color map.
+
+    Raises
+    ------
+    ValueError
+       If you
+    """
+    if name not in cmap_d:
+        return
+    if name in globals():
+        raise ValueError(f"Can not deregister {name} which is a builtin "
+                         "color map.")
+    cmap_d.pop(name)
+
+
 class ScalarMappable:
     """
     This is a mixin class to support scalar data to RGBA mapping.
 
@@ -13,3 +13,15 @@ def test_register_cmap():
 
     with pytest.warns(UserWarning):
         mcm.register_cmap('viridis'[::-1], mcm.get_cmap('viridis'))
+
+
+    mcm.deregister_cmap('viridis'[::-1])
+    with pytest.raises(ValueError):
+        mcm.get_cmap('viridis'[::-1])
+    # test that second time is error free
+    mcm.deregister_cmap('viridis'[::-1])
+
+
+def test_deregister_cmap():
+    with pytest.raises(ValueError):
+        mcm.deregister_cmap('viridis')