diff --git a/acme/src/acme/__init__.py b/acme/src/acme/__init__.py
index 1e21b5896..9a0f5d6e0 100644
--- a/acme/src/acme/__init__.py
+++ b/acme/src/acme/__init__.py
@@ -6,6 +6,7 @@ This module is an implementation of the `ACME protocol`_.
 
 """
 import sys
+import warnings
 
 # This code exists to keep backwards compatibility with people using acme.jose
 # before it became the standalone josepy package.
@@ -19,3 +20,10 @@ for mod in list(sys.modules):
     # preserved (acme.jose.* is josepy.*)
     if mod == 'josepy' or mod.startswith('josepy.'):
         sys.modules['acme.' + mod.replace('josepy', 'jose', 1)] = sys.modules[mod]
+
+if sys.version_info[:2] == (3, 9):
+    warnings.warn(
+            "Python 3.9 support will be dropped in the next planned release of "
+            "acme. Please upgrade your Python version.",
+            DeprecationWarning,
+    )  # pragma: no cover
diff --git a/certbot/src/certbot/__init__.py b/certbot/src/certbot/__init__.py
index 19465f97c..b8ac7c9d6 100644
--- a/certbot/src/certbot/__init__.py
+++ b/certbot/src/certbot/__init__.py
@@ -1,4 +1,14 @@
 """Certbot client."""
+import sys
+import warnings
 
 # version number like 1.2.3a0, must have at least 2 parts, like 1.2
 __version__ = '4.2.0.dev0'
+
+
+if sys.version_info[:2] == (3, 9):
+    warnings.warn(
+            "Python 3.9 support will be dropped in the next planned release of "
+            "certbot. Please upgrade your Python version.",
+            DeprecationWarning,
+    )  # pragma: no cover
diff --git a/certbot/src/certbot/_internal/main.py b/certbot/src/certbot/_internal/main.py
index 84175b6a4..c6e80fbc5 100644
--- a/certbot/src/certbot/_internal/main.py
+++ b/certbot/src/certbot/_internal/main.py
@@ -1867,6 +1867,10 @@ def main(cli_args: Optional[List[str]] = None) -> Optional[Union[str, int]]:
         if config.func != plugins_cmd:  # pylint: disable=comparison-with-callable
             raise
 
+    if sys.version_info[:2] == (3, 9):
+        logger.warning("Python 3.9 support will be dropped in the next planned release "
+                       "of Certbot - please upgrade your Python version.")
+
     with make_displayer(config) as displayer:
         display_obj.set_display(displayer)
 
diff --git a/newsfragments/10390.changed b/newsfragments/10390.changed
new file mode 100644
index 000000000..37a988e3b
--- /dev/null
+++ b/newsfragments/10390.changed
@@ -0,0 +1 @@
+Support for Python 3.9 was deprecated and will be removed in our next planned release.
diff --git a/pytest.ini b/pytest.ini
index 4785e2097..1edd7444a 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -29,6 +29,7 @@
 #     See https://github.com/certbot/certbot/issues/10291.
 # 13) Removing probe_sni from public acme, since it's only used in certbot-compatibility-test
 #     after TLS-ALPN support is removed.
+# 14) Ignore our own DeprecationWarning about Python 3.9 soon to be dropped.
 filterwarnings =
     error
     ignore:.*rsyncdir:DeprecationWarning
@@ -44,3 +45,4 @@ filterwarnings =
     ignore:TLSServer is deprecated:DeprecationWarning
     ignore:enforce_openssl_binary_usage parameter is deprecated:DeprecationWarning
     ignore:probe_sni is deprecated:DeprecationWarning
+    ignore:Python 3.9 support will be dropped:DeprecationWarning