diff --git a/doc/source/whatsnew/v2.1.0.rst b/doc/source/whatsnew/v2.1.0.rst
index 201bf23ea2339..b4b606e349f51 100644
--- a/doc/source/whatsnew/v2.1.0.rst
+++ b/doc/source/whatsnew/v2.1.0.rst
@@ -352,7 +352,7 @@ Conversion
 - Bug in :meth:`DataFrame.__repr__` incorrectly raising a ``TypeError`` when the dtype of a column is ``np.record`` (:issue:`48526`)
 - Bug in :meth:`DataFrame.info` raising  ``ValueError`` when ``use_numba`` is set (:issue:`51922`)
 - Bug in :meth:`DataFrame.insert` raising ``TypeError`` if ``loc`` is ``np.int64`` (:issue:`53193`)
--
+- Bug in :meth:`datetimes._guess_datetime_format` if contains "AM" / "PM" tokens (:issue:`53147`)
 
 Strings
 ^^^^^^^
diff --git a/pandas/_libs/tslibs/parsing.pyx b/pandas/_libs/tslibs/parsing.pyx
index 0cf03ecf34c41..c7a3da3d378b7 100644
--- a/pandas/_libs/tslibs/parsing.pyx
+++ b/pandas/_libs/tslibs/parsing.pyx
@@ -908,7 +908,6 @@ def guess_datetime_format(dt_str: str, bint dayfirst=False) -> str | None:
         (("tzinfo",), "%Z", 0),
         (("day_of_week",), "%a", 0),
         (("day_of_week",), "%A", 0),
-        (("meridiem",), "%p", 0),
     ]
 
     if dayfirst:
diff --git a/pandas/tests/tools/test_to_datetime.py b/pandas/tests/tools/test_to_datetime.py
index 0b5696116e610..b8079375b2aaf 100644
--- a/pandas/tests/tools/test_to_datetime.py
+++ b/pandas/tests/tools/test_to_datetime.py
@@ -2942,6 +2942,7 @@ class TestDatetimeParsingWrappers:
             ("2005-11-09 10:15", datetime(2005, 11, 9, 10, 15)),
             ("2005-11-09 08H", datetime(2005, 11, 9, 8, 0)),
             ("2005/11/09 10:15", datetime(2005, 11, 9, 10, 15)),
+            ("2005/11/09 10:15:32", datetime(2005, 11, 9, 10, 15, 32)),
             ("2005/11/09 08H", datetime(2005, 11, 9, 8, 0)),
             ("Thu Sep 25 10:36:28 2003", datetime(2003, 9, 25, 10, 36, 28)),
             ("Thu Sep 25 2003", datetime(2003, 9, 25)),
diff --git a/pandas/tests/tslibs/test_parsing.py b/pandas/tests/tslibs/test_parsing.py
index 587527c2058d7..c6bf667ddd70c 100644
--- a/pandas/tests/tslibs/test_parsing.py
+++ b/pandas/tests/tslibs/test_parsing.py
@@ -208,8 +208,10 @@ def test_parsers_month_freq(date_str, expected):
         ("2011-12-30T00:00:00.000000+9:0", "%Y-%m-%dT%H:%M:%S.%f%z"),
         ("2011-12-30T00:00:00.000000+09:", None),
         ("2011-12-30 00:00:00.000000", "%Y-%m-%d %H:%M:%S.%f"),
-        ("Tue 24 Aug 2021 01:30:48 AM", "%a %d %b %Y %H:%M:%S %p"),
-        ("Tuesday 24 Aug 2021 01:30:48 AM", "%A %d %b %Y %H:%M:%S %p"),
+        ("Tue 24 Aug 2021 01:30:48", "%a %d %b %Y %H:%M:%S"),
+        ("Tuesday 24 Aug 2021 01:30:48", "%A %d %b %Y %H:%M:%S"),
+        ("Tue 24 Aug 2021 01:30:48 AM", None),
+        ("Tuesday 24 Aug 2021 01:30:48 AM", None),
         ("27.03.2003 14:55:00.000", "%d.%m.%Y %H:%M:%S.%f"),  # GH50317
     ],
 )