diff --git a/Doc/library/xml.etree.elementtree.rst b/Doc/library/xml.etree.elementtree.rst
index 881708a4dd7..cbbc87b4721 100644
--- a/Doc/library/xml.etree.elementtree.rst
+++ b/Doc/library/xml.etree.elementtree.rst
@@ -656,6 +656,10 @@ Functions
    .. versionchanged:: 3.13
       Added the :meth:`!close` method.
 
+   .. versionchanged:: next
+      A :exc:`ResourceWarning` is now emitted if the iterator opened a file
+      and is not explicitly closed.
+
 
 .. function:: parse(source, parser=None)
 
diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index 895616e3049..31594a2e70b 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -1244,3 +1244,9 @@ that may require changes to your code.
 
 * :meth:`~mmap.mmap.resize` has been removed on platforms that don't support the
   underlying syscall, instead of raising a :exc:`SystemError`.
+
+* Resource warning is now emitted for unclosed
+  :func:`xml.etree.ElementTree.iterparse` iterator if it opened a file.
+  Use its :meth:`!close` method or the :func:`contextlib.closing` context
+  manager to close it.
+  (Contributed by Osama Abdelkader and Serhiy Storchaka in :gh:`140601`.)
diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 25c084c8b9c..87811199706 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -1436,17 +1436,39 @@ def test_nonexistent_file(self):
 
     def test_resource_warnings_not_exhausted(self):
         # Not exhausting the iterator still closes the underlying file (bpo-43292)
+        # Not closing before del should emit ResourceWarning
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
+            it.close()
             del it
             gc_collect()
 
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
+            del it
+            gc_collect()
+        # Not 'unclosed file'.
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
+
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
+            action, elem = next(it)
+            it.close()
+            self.assertEqual((action, elem.tag), ('end', 'element'))
+            del it, elem
+            gc_collect()
+
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
             action, elem = next(it)
             self.assertEqual((action, elem.tag), ('end', 'element'))
             del it, elem
             gc_collect()
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
 
     def test_resource_warnings_failed_iteration(self):
         self.addCleanup(os_helper.unlink, TESTFN)
@@ -1461,16 +1483,41 @@ def test_resource_warnings_failed_iteration(self):
                 next(it)
             self.assertEqual(str(cm.exception),
                     'junk after document element: line 1, column 12')
+            it.close()
             del cm, it
             gc_collect()
 
+        it = ET.iterparse(TESTFN)
+        action, elem = next(it)
+        self.assertEqual((action, elem.tag), ('end', 'document'))
+        with self.assertWarns(ResourceWarning) as wm:
+            with self.assertRaises(ET.ParseError) as cm:
+                next(it)
+            self.assertEqual(str(cm.exception),
+                    'junk after document element: line 1, column 12')
+            del cm, it
+            gc_collect()
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(TESTFN), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
+
     def test_resource_warnings_exhausted(self):
         it = ET.iterparse(SIMPLE_XMLFILE)
         with warnings_helper.check_no_resource_warning(self):
             list(it)
+            it.close()
             del it
             gc_collect()
 
+        it = ET.iterparse(SIMPLE_XMLFILE)
+        with self.assertWarns(ResourceWarning) as wm:
+            list(it)
+            del it
+            gc_collect()
+        self.assertIn('unclosed iterparse iterator', str(wm.warning))
+        self.assertIn(repr(SIMPLE_XMLFILE), str(wm.warning))
+        self.assertEqual(wm.filename, __file__)
+
     def test_close_not_exhausted(self):
         iterparse = ET.iterparse
 
diff --git a/Lib/xml/etree/ElementTree.py b/Lib/xml/etree/ElementTree.py
index dafe5b1b8a0..d8c0b1b6216 100644
--- a/Lib/xml/etree/ElementTree.py
+++ b/Lib/xml/etree/ElementTree.py
@@ -1261,16 +1261,20 @@ def iterator(source):
     gen = iterator(source)
     class IterParseIterator(collections.abc.Iterator):
         __next__ = gen.__next__
+
         def close(self):
+            nonlocal close_source
             if close_source:
                 source.close()
+                close_source = False
             gen.close()
 
-        def __del__(self):
-            # TODO: Emit a ResourceWarning if it was not explicitly closed.
-            # (When the close() method will be supported in all maintained Python versions.)
+        def __del__(self, _warn=warnings.warn):
             if close_source:
-                source.close()
+                try:
+                    _warn(f"unclosed iterparse iterator {source.name!r}", ResourceWarning, stacklevel=2)
+                finally:
+                    source.close()
 
     it = IterParseIterator()
     it.root = None
diff --git a/Misc/NEWS.d/next/Library/2025-10-25-22-55-07.gh-issue-140601.In3MlS.rst b/Misc/NEWS.d/next/Library/2025-10-25-22-55-07.gh-issue-140601.In3MlS.rst
new file mode 100644
index 00000000000..72666bb8224
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-10-25-22-55-07.gh-issue-140601.In3MlS.rst
@@ -0,0 +1,4 @@
+:func:`xml.etree.ElementTree.iterparse` now emits a :exc:`ResourceWarning`
+when the iterator is not explicitly closed and was opened with a filename.
+This helps developers identify and fix resource leaks. Patch by Osama
+Abdelkader.