diff --git a/docs/conf.py b/docs/conf.py
index 2aab2f2f22a..47691fb1122 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -63,7 +63,6 @@
 warnings.filterwarnings("error", category=SunpyPendingDeprecationWarning)
 warnings.filterwarnings("error", category=MatplotlibDeprecationWarning)
 warnings.filterwarnings("error", category=AstropyDeprecationWarning)
-warnings.filterwarnings("ignore", message="The `sunpy.io.cdf` module is deprecated",category=SunpyDeprecationWarning)
 warnings.filterwarnings("ignore", message="The `sunpy.io.jp2` module is deprecated",category=SunpyDeprecationWarning)
 warnings.filterwarnings("ignore", message="The `sunpy.io.file_tools` module is deprecated",category=SunpyDeprecationWarning)
 
diff --git a/sunpy/io/_cdf.py b/sunpy/io/_cdf.py
index 34489de05c7..07077b91e68 100644
--- a/sunpy/io/_cdf.py
+++ b/sunpy/io/_cdf.py
@@ -1,10 +1,5 @@
 """
 This module provides a CDF file reader for internal use.
-
-.. warning::
-
-    ``sunpy.io.cdf`` is deprecated, and will be removed in sunpy 5.1. This is
-    because it was designed for internal use only.
 """
 import cdflib
 import numpy as np
diff --git a/sunpy/io/cdf.py b/sunpy/io/cdf.py
deleted file mode 100644
index 483a494cbbd..00000000000
--- a/sunpy/io/cdf.py
+++ /dev/null
@@ -1,9 +0,0 @@
-from sunpy.util.exceptions import warn_deprecated
-from . import _cdf
-from ._cdf import *  # NOQA
-
-__doc__ = _cdf.__doc__
-__all__ = _cdf.__all__
-
-warn_deprecated("The `sunpy.io.cdf` module is deprecated, as it was designed "
-                "for internal use.")
diff --git a/sunpy/io/tests/test_cdf.py b/sunpy/io/tests/test_cdf.py
index a6d46fd5355..9cc776df27f 100644
--- a/sunpy/io/tests/test_cdf.py
+++ b/sunpy/io/tests/test_cdf.py
@@ -1,4 +1,3 @@
-import importlib
 
 import numpy as np
 
@@ -24,8 +23,3 @@ def test_read_cdf():
     assert col.unit == u.Unit("1 / (cm2 MeV s sr)")
     # Check that fillvals are replaced by NaN
     assert np.sum(np.isnan(col)) == 189
-
-
-def test_old_import():
-    lib = importlib.import_module("sunpy.io.cdf")
-    assert lib.read_cdf is read_cdf
diff --git a/sunpy/timeseries/tests/test_timeseries_factory.py b/sunpy/timeseries/tests/test_timeseries_factory.py
index f3c7a2243b6..20bb610569c 100644
--- a/sunpy/timeseries/tests/test_timeseries_factory.py
+++ b/sunpy/timeseries/tests/test_timeseries_factory.py
@@ -124,7 +124,7 @@ def test_read_cdf_empty_variable():
                                    a.cdaweb.Dataset('AC_H6_SWI'))
     filename = Fido.fetch(result[0, 0])
 
-    # Temporarily reset sunpy.io.cdf registry of known unit conversions
+    # Temporarily reset sunpy.io._cdf registry of known unit conversions
     import sunpy.io._cdf as sunpy_cdf
     known_units = sunpy_cdf._known_units
     sunpy_cdf._known_units = {}