diff --git a/Modules/_xxtestfuzz/dictionaries/fuzz_datetime.dict b/Modules/_xxtestfuzz/dictionaries/fuzz_datetime.dict
new file mode 100644
index 00000000000000..6824d4dc2884f2
--- /dev/null
+++ b/Modules/_xxtestfuzz/dictionaries/fuzz_datetime.dict
@@ -0,0 +1,33 @@
+# ISO-8601 tokens for date/time/datetime.fromisoformat
+"T"
+"Z"
+"z"
+"+01:00"
+"+01:00:30"
+"-05:30"
+"+0000"
+"+01"
+"2024-01-15"
+"2024-01-15T10:30"
+"2024-01-15 10:30:00"
+"10:30"
+"10:30:00"
+"10:30:00.123456"
+"10:30:00,5"
+".123456"
+",123"
+"24:00"
+"00:00"
+"W"
+"-W"
+"2024-W03-1"
+"2024-W03"
+"2024-021"
+"0001-01-01"
+"9999-12-31"
+"23:59:59.999999"
+"+23:59"
+"-23:59"
+"hh"
+"mm"
+"ss"
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_0 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_0
new file mode 100644
index 00000000000000..8ace4123371004
Binary files /dev/null and b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_0 differ
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_1 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_1
new file mode 100644
index 00000000000000..032c919709146c
Binary files /dev/null and b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_1 differ
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_2 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_2
new file mode 100644
index 00000000000000..6bcac16374b317
Binary files /dev/null and b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_2 differ
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_3 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_3
new file mode 100644
index 00000000000000..54719f4712541a
Binary files /dev/null and b/Modules/_xxtestfuzz/fuzz_datetime_corpus/date_3 differ
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_0 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_0
new file mode 100644
index 00000000000000..ef057eeee8b62a
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_0
@@ -0,0 +1 @@
+2024-01-15T10:30
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_1 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_1
new file mode 100644
index 00000000000000..7d23e84d3f3f61
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_1
@@ -0,0 +1 @@
+2024-01-15 10:30:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_2 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_2
new file mode 100644
index 00000000000000..e67caaa770fedf
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_2
@@ -0,0 +1 @@
+2024-01-15T10:30:00.123456
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_3 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_3
new file mode 100644
index 00000000000000..fa07490b71ff50
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_3
@@ -0,0 +1 @@
+2024-01-15T10:30:00+01:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_4 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_4
new file mode 100644
index 00000000000000..3aee0de4035a19
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_4
@@ -0,0 +1 @@
+2024-01-15T10:30:00.123456-05:30
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_5 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_5
new file mode 100644
index 00000000000000..d7091cf475c968
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_5
@@ -0,0 +1 @@
+0001-01-01T00:00:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_6 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_6
new file mode 100644
index 00000000000000..7cae7482480211
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_6
@@ -0,0 +1 @@
+9999-12-31T23:59:59.999999+00:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_7 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_7
new file mode 100644
index 00000000000000..bbd0b36b0c5d01
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/datetime_7
@@ -0,0 +1 @@
+2024-06-01T12:00:00.000001+02:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_0 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_0
new file mode 100644
index 00000000000000..c75d29d33adc3d
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_0
@@ -0,0 +1 @@
+
10:30
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_1 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_1
new file mode 100644
index 00000000000000..c6490577325e9a
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_1
@@ -0,0 +1 @@
+
10:30:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_2 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_2
new file mode 100644
index 00000000000000..348f88e6e5af95
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_2
@@ -0,0 +1 @@
+
10:30:00.123456
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_3 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_3
new file mode 100644
index 00000000000000..5ddcd9eadef3ce
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_3
@@ -0,0 +1 @@
+
10:30:00,5
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_4 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_4
new file mode 100644
index 00000000000000..188833d119b8c5
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_4
@@ -0,0 +1 @@
+
00:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_5 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_5
new file mode 100644
index 00000000000000..15612f2963c805
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_5
@@ -0,0 +1 @@
+
23:59:59.999999
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_6 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_6
new file mode 100644
index 00000000000000..bd8c2a4dfaf752
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_6
@@ -0,0 +1 @@
+
10:30+01:00
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_7 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_7
new file mode 100644
index 00000000000000..e492887e1a4532
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_7
@@ -0,0 +1 @@
+
10:30:00-05:30
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_8 b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_8
new file mode 100644
index 00000000000000..dd2c6ce25cf9db
--- /dev/null
+++ b/Modules/_xxtestfuzz/fuzz_datetime_corpus/time_8
@@ -0,0 +1 @@
+
10:30:00.123456+01:00:30
\ No newline at end of file
diff --git a/Modules/_xxtestfuzz/fuzz_tests.txt b/Modules/_xxtestfuzz/fuzz_tests.txt
index ea6f982eefc9da..86df736548f7c8 100644
--- a/Modules/_xxtestfuzz/fuzz_tests.txt
+++ b/Modules/_xxtestfuzz/fuzz_tests.txt
@@ -9,3 +9,4 @@ fuzz_struct_unpack
 fuzz_ast_literal_eval
 fuzz_elementtree_parsewhole
 fuzz_pycompile
+fuzz_datetime
diff --git a/Modules/_xxtestfuzz/fuzzer.c b/Modules/_xxtestfuzz/fuzzer.c
index 8c2d0e93cd72d4..58e86af1aadc99 100644
--- a/Modules/_xxtestfuzz/fuzzer.c
+++ b/Modules/_xxtestfuzz/fuzzer.c
@@ -595,6 +595,145 @@ static int _run_fuzz(const uint8_t *data, size_t size, int(*fuzzer)(const char*
     return rv;
 }
 
+#define MAX_DATETIME_TEST_SIZE 0x10000
+
+/* Fuzz the C ISO-8601 fast parsers and date/time arithmetic: date,
+   time and datetime fromisoformat() (all parsing lives in
+   Modules/_datetimemodule.c), isoformat() round-tripping as a property
+   (documented inverse), and timedelta addition/subtraction to drive the
+   C normalisation and overflow-checking paths. */
+static PyObject* datetime_module = NULL;
+static PyObject* date_type = NULL;
+static PyObject* time_type = NULL;
+static PyObject* datetime_type = NULL;
+static PyObject* timedelta_type = NULL;
+
+/* Called by LLVMFuzzerTestOneInput for initialization */
+static int init_datetime(void) {
+    datetime_module = PyImport_ImportModule("datetime");
+    if (datetime_module == NULL) {
+        return 0;
+    }
+    date_type = PyObject_GetAttrString(datetime_module, "date");
+    time_type = PyObject_GetAttrString(datetime_module, "time");
+    datetime_type = PyObject_GetAttrString(datetime_module, "datetime");
+    timedelta_type = PyObject_GetAttrString(datetime_module, "timedelta");
+    return (date_type != NULL && time_type != NULL &&
+            datetime_type != NULL && timedelta_type != NULL);
+}
+
+/* Call <type>.fromisoformat(s); returns new reference or NULL */
+static PyObject* datetime_fromiso_format(PyObject* type, PyObject* s) {
+    return PyObject_CallMethod(type, "fromisoformat", "O", s);
+}
+
+/* Fuzz date/time/datetime.fromisoformat(x) + arithmetic */
+static int fuzz_datetime(const char* data, size_t size) {
+    if (size < 2 || size > MAX_DATETIME_TEST_SIZE) {
+        return 0;
+    }
+    /* First byte selects the parser, second drives the timedelta. */
+    unsigned char op = (unsigned char) data[0];
+    unsigned char amount = (unsigned char) data[1];
+    data += 2;
+    size -= 2;
+
+    PyObject* s = PyUnicode_FromStringAndSize(data, size);
+    if (s == NULL) {
+        if (PyErr_ExceptionMatches(PyExc_UnicodeDecodeError)) {
+            PyErr_Clear();
+        }
+        return 0;
+    }
+
+    PyObject* parsed = NULL;
+    switch (op % 3) {
+        case 0:
+            parsed = datetime_fromiso_format(date_type, s);
+            break;
+        case 1:
+            parsed = datetime_fromiso_format(time_type, s);
+            break;
+        default:
+            parsed = datetime_fromiso_format(datetime_type, s);
+            break;
+    }
+    if (parsed == NULL) {
+        /* Invalid ISO strings are the expected failure mode; anything
+           else is caught by _run_fuzz's last-ditch check. */
+        if (PyErr_ExceptionMatches(PyExc_ValueError) ||
+            PyErr_ExceptionMatches(PyExc_TypeError))
+        {
+            PyErr_Clear();
+        }
+        Py_DECREF(s);
+        return 0;
+    }
+
+    /* Property: isoformat() output must parse back to an equal object
+       (fromisoformat is the documented inverse of isoformat). A failure
+       or mismatch is a genuine logic bug, not a harness fault. */
+    PyObject* iso = PyObject_CallMethod(parsed, "isoformat", NULL);
+    if (iso == NULL) {
+        PyErr_Clear();
+    } else {
+        PyObject* reparsed = datetime_fromiso_format(
+            op % 3 == 0 ? date_type : (op % 3 == 1 ? time_type : datetime_type),
+            iso);
+        if (reparsed == NULL) {
+            PyErr_Print();
+            abort();
+        }
+        int equal = PyObject_RichCompareBool(parsed, reparsed, Py_EQ);
+        if (equal < 0) {
+            PyErr_Clear();
+        } else if (equal == 0) {
+            PyErr_SetString(PyExc_AssertionError,
+                            "isoformat/fromisoformat round-trip mismatch");
+            PyErr_Print();
+            abort();
+        }
+        Py_DECREF(reparsed);
+        Py_DECREF(iso);
+
+        /* Exercise C arithmetic and normalisation with a fuzzed timedelta.
+           (time objects reject +/- with TypeError: expected and cleared.) */
+        PyObject* td = PyObject_CallFunction(timedelta_type, "iii",
+                                             amount % 30, amount % 60,
+                                             amount % 1000000);
+        if (td == NULL) {
+            PyErr_Clear();
+        } else {
+            PyObject* shifted = PyNumber_Add(parsed, td);
+            if (shifted == NULL) {
+                if (PyErr_ExceptionMatches(PyExc_TypeError) ||
+                    PyErr_ExceptionMatches(PyExc_OverflowError))
+                {
+                    PyErr_Clear();
+                }
+            } else {
+                Py_DECREF(shifted);
+            }
+            PyObject* shifted_back = PyNumber_Subtract(parsed, td);
+            if (shifted_back == NULL) {
+                if (PyErr_ExceptionMatches(PyExc_TypeError) ||
+                    PyErr_ExceptionMatches(PyExc_OverflowError))
+                {
+                    PyErr_Clear();
+                }
+            } else {
+                Py_DECREF(shifted_back);
+            }
+            Py_DECREF(td);
+        }
+    }
+
+    Py_DECREF(parsed);
+    Py_DECREF(s);
+    return 0;
+}
+
+
 /* CPython generates a lot of leak warnings for whatever reason. */
 int __lsan_is_turned_off(void) { return 1; }
 
@@ -726,6 +865,17 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
 #endif
 #if !defined(_Py_FUZZ_ONE) || defined(_Py_FUZZ_fuzz_pycompile)
     rv |= _run_fuzz(data, size, fuzz_pycompile);
+#endif
+#if !defined(_Py_FUZZ_ONE) || defined(_Py_FUZZ_fuzz_datetime)
+    static int DATETIME_INITIALIZED = 0;
+    if (!DATETIME_INITIALIZED && !init_datetime()) {
+        PyErr_Print();
+        abort();
+    } else {
+        DATETIME_INITIALIZED = 1;
+    }
+
+    rv |= _run_fuzz(data, size, fuzz_datetime);
 #endif
   return rv;
 }