python
diff --git a/Lib/re/_properties.py b/Lib/re/_properties.py
@@ -209,11 +209,11 @@ def _analytic_ranges():
 
 
 def _normalize(name):
-    # Unicode property and value names are matched loosely: case, spaces,
-    # hyphens and underscores are not significant, and an initial "is" prefix
-    # is ignored (UAX #44 5.9, "Matching Rules", UAX44-LM3;
+    # Unicode property and value names are matched loosely: case, whitespace
+    # and hyphens and underscores are not significant, and an initial "is"
+    # prefix is ignored (UAX #44 5.9, "Matching Rules", UAX44-LM3;
     # https://www.unicode.org/reports/tr44/).
-    name = name.lower().replace("_", "").replace("-", "").replace(" ", "")
+    name = "".join(ch for ch in name.lower() if ch not in " \t\n\r\f\v_-")
     # Strip a leading "is", unless "is" is the whole name and so not a prefix
     # (e.g. the Line_Break value lb=IS).
     if name != "is":

diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
@@ -929,6 +929,12 @@ def test_property_escapes(self):
         self.assertTrue(re.fullmatch(r'\p{General_Category=Lu}+', 'ABC'))
         self.assertTrue(re.fullmatch(r'\p{ lu }+', 'ABC'))
         self.assertTrue(re.fullmatch(r'\p{LU}+', 'ABC'))
+        # All ASCII whitespace is ignored, not just spaces (UAX44-LM3;
+        # gh-156185).
+        for ws in " \t\n\r\f\v":
+            with self.subTest(ws=ws):
+                self.assertTrue(re.fullmatch(r'\p{L%su}+' % ws, 'ABC'))
+                self.assertTrue(re.fullmatch(r'\p{gc%s=L%su}+' % (ws, ws), 'ABC'))
         # An initial "is" prefix is ignored (UAX44-LM3), on the property name
         # and on a gc value; "is" alone is not a prefix (cf. lb=IS).
         self.assertTrue(re.fullmatch(r'\p{isLu}+', 'ABC'))

diff --git a/Misc/NEWS.d/next/Library/2026-08-24-10-30-00.gh-issue-156185.a1b2c3.rst b/Misc/NEWS.d/next/Library/2026-08-24-10-30-00.gh-issue-156185.a1b2c3.rst
@@ -0,0 +1,3 @@
+``\p{property}`` and ``\p{property=value}`` regex escapes now ignore all
+ASCII whitespace in property and value names, as documented, instead of
+only spaces.