diff --git a/rest_framework/renderers.py b/rest_framework/renderers.py
index c471e1f84..4f3fce0ab 100644
--- a/rest_framework/renderers.py
+++ b/rest_framework/renderers.py
@@ -347,7 +347,10 @@ class HTMLFormRenderer(BaseRenderer):
             # followed by optional ":ss" or ":ss.SSS", so keep only the first three
             # digits of milliseconds to avoid browser console error.
             datetime_parts = field.value.split(".")
-            field.value = f"{datetime_parts[0]}.{datetime_parts[1][:3]}"
+            if len(datetime_parts) > 1:
+                field.value = f"{datetime_parts[0]}.{datetime_parts[1][:3]}"
+            else:
+                field.value = field.value.rstrip('Z')
 
         if 'template' in style:
             template_name = style['template']
diff --git a/tests/test_renderers.py b/tests/test_renderers.py
index e76908e7e..d723f90c2 100644
--- a/tests/test_renderers.py
+++ b/tests/test_renderers.py
@@ -489,8 +489,9 @@ class TestHiddenFieldHTMLFormRenderer(TestCase):
         assert rendered == ''
 
 
+@override_settings(TIME_ZONE='UTC', USE_TZ=True)
 class TestDateTimeFieldHTMLFormRender(TestCase):
-    def test_datetime_field_rendering(self):
+    def test_datetime_field_rendering_milliseconds(self):
         class TestSerializer(serializers.Serializer):
             appointment = serializers.DateTimeField()
 
@@ -505,6 +506,36 @@ class TestDateTimeFieldHTMLFormRender(TestCase):
             rendered
         )
 
+    def test_datetime_field_rendering_no_milliseconds(self):
+        class TestSerializer(serializers.Serializer):
+            appointment = serializers.DateTimeField()
+
+        appointment = datetime(2024, 12, 24, 0, 55, 30, 0)
+        serializer = TestSerializer(data={"appointment": appointment})
+        serializer.is_valid()
+        renderer = HTMLFormRenderer()
+        field = serializer['appointment']
+        rendered = renderer.render_field(field, {})
+        self.assertInHTML(
+            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:30">',
+            rendered
+        )
+
+    def test_datetime_field_rendering_no_seconds_and_milliseconds(self):
+        class TestSerializer(serializers.Serializer):
+            appointment = serializers.DateTimeField()
+
+        appointment = datetime(2024, 12, 24, 0, 55, 0, 0)
+        serializer = TestSerializer(data={"appointment": appointment})
+        serializer.is_valid()
+        renderer = HTMLFormRenderer()
+        field = serializer['appointment']
+        rendered = renderer.render_field(field, {})
+        self.assertInHTML(
+            '<input name="appointment" class="form-control" type="datetime-local" value="2024-12-24T00:55:00">',
+            rendered
+        )
+
 
 class TestHTMLFormRenderer(TestCase):
     def setUp(self):