diff --git a/doc/api/next_api_changes/deprecations.rst b/doc/api/next_api_changes/deprecations.rst
index 4719e944aedf..98b556bf3fa4 100644
--- a/doc/api/next_api_changes/deprecations.rst
+++ b/doc/api/next_api_changes/deprecations.rst
@@ -163,3 +163,9 @@ This ticker is deprecated.
 *required*, *forbidden* and *allowed* parameters of `.cbook.normalize_kwargs`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 These parameters are deprecated.
+
+The ``TTFPATH`` and ``AFMPATH`` environment variables
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Support for the (undocumented) ``TTFPATH`` and ``AFMPATH`` environment
+variables is deprecated.  Additional fonts may be registered using
+``matplotlib.font_manager.fontManager.addfont()``.
diff --git a/lib/matplotlib/font_manager.py b/lib/matplotlib/font_manager.py
index 5033fe550592..bea02d5856c3 100644
--- a/lib/matplotlib/font_manager.py
+++ b/lib/matplotlib/font_manager.py
@@ -971,6 +971,9 @@ def __init__(self, size=None, weight='normal'):
                     paths.extend(ttfpath.split(':'))
                 else:
                     paths.append(ttfpath)
+                cbook.warn_deprecated(
+                    "3.3", name=pathname, obj_type="environment variable",
+                    alternative="FontManager.addfont()")
         _log.debug('font search path %s', str(paths))
         #  Load TrueType fonts and create font dictionary.