diff --git a/doc/api/api_changes_3.3/deprecations.rst b/doc/api/api_changes_3.3/deprecations.rst
index a1c40be2b6d6..adf6337deca9 100644
--- a/doc/api/api_changes_3.3/deprecations.rst
+++ b/doc/api/api_changes_3.3/deprecations.rst
@@ -455,3 +455,8 @@ replaced by calls to ``draw_idle()`` on the corresponding canvas.
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 The ``add_checker`` and ``check_update`` methods and ``update_dict`` attribute
 of `.ScalarMappable` are deprecated.
+
+``ColorbarBase`` parameters will become keyword-only
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+All parameters of ``ColorbarBase``, except for the first (*ax*), will become
+keyword-only, consistently with ``Colorbar``.
diff --git a/lib/matplotlib/colorbar.py b/lib/matplotlib/colorbar.py
index 09e7d3bd9e69..b49451e67e89 100644
--- a/lib/matplotlib/colorbar.py
+++ b/lib/matplotlib/colorbar.py
@@ -394,6 +394,7 @@ class ColorbarBase:
 
     n_rasterize = 50  # rasterize solids if number of colors >= n_rasterize
 
+    @cbook._make_keyword_only("3.3", "cmap")
     def __init__(self, ax, cmap=None,
                  norm=None,
                  alpha=None,
diff --git a/lib/matplotlib/tests/test_colorbar.py b/lib/matplotlib/tests/test_colorbar.py
index 61b3efa3d3de..2a234cf7c0e9 100644
--- a/lib/matplotlib/tests/test_colorbar.py
+++ b/lib/matplotlib/tests/test_colorbar.py
@@ -226,7 +226,7 @@ def test_remove_from_figure(use_gridspec):
 def test_colorbarbase():
     # smoke test from #3805
     ax = plt.gca()
-    ColorbarBase(ax, plt.cm.bone)
+    ColorbarBase(ax, cmap=plt.cm.bone)
 
 
 @image_comparison(['colorbar_closed_patch'], remove_text=True)