diff --git a/Doc/library/re.rst b/Doc/library/re.rst
index d8ead68..07623c9 100644
--- a/Doc/library/re.rst
+++ b/Doc/library/re.rst
@@ -414,17 +414,24 @@
 accepted by the regular expression parser::
 
    \a      \b      \f      \n
-   \r      \t      \v      \x
-   \\
+   \r      \t      \u      \U
+   \v      \x      \\
 
 (Note that ``\b`` is used to represent word boundaries, and means "backspace"
 only inside character classes.)
 
+``'\u'`` and ``'\U'`` escape sequences are only recognized in Unicode
+patterns.  In bytes patterns they are not treated specially.
+
 Octal escapes are included in a limited form.  If the first digit is a 0, or if
 there are three octal digits, it is considered an octal escape. Otherwise, it is
 a group reference.  As for string literals, octal escapes are always at most
 three digits in length.
 
+.. versionchanged:: 3.3
+   The ``'\u'`` and ``'\U'`` escape sequences have been added.
+
+
 
 .. _contents-of-module-re:
 
diff --git a/Lib/sre_parse.py b/Lib/sre_parse.py
index ae63c31..d358646 100644
--- a/Lib/sre_parse.py
+++ b/Lib/sre_parse.py
@@ -177,6 +177,7 @@
 
 class Tokenizer:
     def __init__(self, string):
+        self.istext = isinstance(string, str)
         self.string = string
         self.index = 0
         self.__next()
@@ -187,14 +188,14 @@
         char = self.string[self.index:self.index+1]
         # Special case for the str8, since indexing returns a integer
         # XXX This is only needed for test_bug_926075 in test_re.py
-        if char and isinstance(char, bytes):
+        if char and not self.istext:
             char = chr(char[0])
         if char == "\\":
             try:
                 c = self.string[self.index + 1]
             except IndexError:
                 raise error("bogus escape (end of line)")
-            if isinstance(self.string, bytes):
+            if not self.istext:
                 c = chr(c)
             char = char + c
         self.index = self.index + len(char)
@@ -209,6 +210,15 @@
         this = self.next
         self.__next()
         return this
+    def getwhile(self, n, charset):
+        result = ''
+        for _ in range(n):
+            c = self.next
+            if c not in charset:
+                break
+            result += c
+            self.__next()
+        return result
     def tell(self):
         return self.index, self.next
     def seek(self, index):
@@ -241,20 +251,30 @@
         c = escape[1:2]
         if c == "x":
             # hexadecimal escape (exactly two digits)
-            while source.next in HEXDIGITS and len(escape) < 4:
-                escape = escape + source.get()
-            escape = escape[2:]
-            if len(escape) != 2:
-                raise error("bogus escape: %s" % repr("\\" + escape))
-            return LITERAL, int(escape, 16) & 0xff
+            escape += source.getwhile(2, HEXDIGITS)
+            if len(escape) != 4:
+                raise ValueError
+            return LITERAL, int(escape[2:], 16) & 0xff
+        elif c == "u" and source.istext:
+            # unicode escape (exactly four digits)
+            escape += source.getwhile(4, HEXDIGITS)
+            if len(escape) != 6:
+                raise ValueError
+            return LITERAL, int(escape[2:], 16)
+        elif c == "U" and source.istext:
+            # unicode escape (exactly eight digits)
+            escape += source.getwhile(8, HEXDIGITS)
+            if len(escape) != 10:
+                raise ValueError
+            c = int(escape[2:], 16)
+            chr(c) # raise ValueError for invalid code
+            return LITERAL, c
         elif c in OCTDIGITS:
             # octal escape (up to three digits)
-            while source.next in OCTDIGITS and len(escape) < 4:
-                escape = escape + source.get()
-            escape = escape[1:]
-            return LITERAL, int(escape, 8) & 0xff
+            escape += source.getwhile(2, OCTDIGITS)
+            return LITERAL, int(escape[1:], 8) & 0xff
         elif c in DIGITS:
-            raise error("bogus escape: %s" % repr(escape))
+            raise ValueError
         if len(escape) == 2:
             return LITERAL, ord(escape[1])
     except ValueError:
@@ -273,15 +293,27 @@
         c = escape[1:2]
         if c == "x":
             # hexadecimal escape
-            while source.next in HEXDIGITS and len(escape) < 4:
-                escape = escape + source.get()
+            escape += source.getwhile(2, HEXDIGITS)
             if len(escape) != 4:
                 raise ValueError
             return LITERAL, int(escape[2:], 16) & 0xff
+        elif c == "u" and source.istext:
+            # unicode escape (exactly four digits)
+            escape += source.getwhile(4, HEXDIGITS)
+            if len(escape) != 6:
+                raise ValueError
+            return LITERAL, int(escape[2:], 16)
+        elif c == "U" and source.istext:
+            # unicode escape (exactly eight digits)
+            escape += source.getwhile(8, HEXDIGITS)
+            if len(escape) != 10:
+                raise ValueError
+            c = int(escape[2:], 16)
+            chr(c) # raise ValueError for invalid code
+            return LITERAL, c
         elif c == "0":
             # octal escape
-            while source.next in OCTDIGITS and len(escape) < 4:
-                escape = escape + source.get()
+            escape += source.getwhile(2, OCTDIGITS)
             return LITERAL, int(escape[1:], 8) & 0xff
         elif c in DIGITS:
             # octal escape *or* decimal group reference (sigh)
diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index 74a7b71..9b0aa75 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -526,24 +526,92 @@
             self.assertNotEqual(re.compile('^pattern$', flag), None)
 
     def test_sre_character_literals(self):
-        for i in [0, 8, 16, 32, 64, 127, 128, 255]:
-            self.assertNotEqual(re.match(r"\%03o" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"\%03o0" % i, chr(i)+"0"), None)
-            self.assertNotEqual(re.match(r"\%03o8" % i, chr(i)+"8"), None)
-            self.assertNotEqual(re.match(r"\x%02x" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"\x%02x0" % i, chr(i)+"0"), None)
-            self.assertNotEqual(re.match(r"\x%02xz" % i, chr(i)+"z"), None)
-        self.assertRaises(re.error, re.match, "\911", "")
+        for i in [0, 8, 16, 32, 64, 127, 128, 255, 256, 0xFFFF, 0x10000, 0x10FFFF]:
+            if i < 256:
+                self.assertIsNotNone(re.match(r"\%03o" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"\%03o0" % i, chr(i)+"0"))
+                self.assertIsNotNone(re.match(r"\%03o8" % i, chr(i)+"8"))
+                self.assertIsNotNone(re.match(r"\x%02x" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"\x%02x0" % i, chr(i)+"0"))
+                self.assertIsNotNone(re.match(r"\x%02xz" % i, chr(i)+"z"))
+            if i < 0x10000:
+                self.assertIsNotNone(re.match(r"\u%04x" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"\u%04x0" % i, chr(i)+"0"))
+                self.assertIsNotNone(re.match(r"\u%04xz" % i, chr(i)+"z"))
+            self.assertIsNotNone(re.match(r"\U%08x" % i, chr(i)))
+            self.assertIsNotNone(re.match(r"\U%08x0" % i, chr(i)+"0"))
+            self.assertIsNotNone(re.match(r"\U%08xz" % i, chr(i)+"z"))
+        self.assertIsNotNone(re.match(r"\0", "\000"))
+        self.assertIsNotNone(re.match(r"\08", "\0008"))
+        self.assertIsNotNone(re.match(r"\01", "\001"))
+        self.assertIsNotNone(re.match(r"\018", "\0018"))
+        self.assertIsNotNone(re.match(r"\567", chr(0o167)))
+        self.assertRaises(re.error, re.match, r"\911", "")
+        self.assertRaises(re.error, re.match, r"\x1", "")
+        self.assertRaises(re.error, re.match, r"\x1z", "")
+        self.assertRaises(re.error, re.match, r"\u123", "")
+        self.assertRaises(re.error, re.match, r"\u123z", "")
+        self.assertRaises(re.error, re.match, r"\U0001234", "")
+        self.assertRaises(re.error, re.match, r"\U0001234z", "")
+        self.assertRaises(re.error, re.match, r"\U00110000", "")
 
     def test_sre_character_class_literals(self):
+        for i in [0, 8, 16, 32, 64, 127, 128, 255, 256, 0xFFFF, 0x10000, 0x10FFFF]:
+            if i < 256:
+                self.assertIsNotNone(re.match(r"[\%o]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\%o8]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\%03o]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\%03o0]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\%03o8]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\x%02x]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\x%02x0]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\x%02xz]" % i, chr(i)))
+            if i < 0x10000:
+                self.assertIsNotNone(re.match(r"[\u%04x]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\u%04x0]" % i, chr(i)))
+                self.assertIsNotNone(re.match(r"[\u%04xz]" % i, chr(i)))
+            self.assertIsNotNone(re.match(r"[\U%08x]" % i, chr(i)))
+            self.assertIsNotNone(re.match(r"[\U%08x0]" % i, chr(i)+"0"))
+            self.assertIsNotNone(re.match(r"[\U%08xz]" % i, chr(i)+"z"))
+        self.assertRaises(re.error, re.match, r"[\911]", "")
+        self.assertRaises(re.error, re.match, r"[\x1z]", "")
+        self.assertRaises(re.error, re.match, r"[\u123z]", "")
+        self.assertRaises(re.error, re.match, r"[\U0001234z]", "")
+        self.assertRaises(re.error, re.match, r"[\U00110000]", "")
+
+    def test_sre_byte_literals(self):
         for i in [0, 8, 16, 32, 64, 127, 128, 255]:
-            self.assertNotEqual(re.match(r"[\%03o]" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"[\%03o0]" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"[\%03o8]" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"[\x%02x]" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"[\x%02x0]" % i, chr(i)), None)
-            self.assertNotEqual(re.match(r"[\x%02xz]" % i, chr(i)), None)
-        self.assertRaises(re.error, re.match, "[\911]", "")
+            self.assertIsNotNone(re.match((r"\%03o" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"\%03o0" % i).encode(), bytes([i])+b"0"))
+            self.assertIsNotNone(re.match((r"\%03o8" % i).encode(), bytes([i])+b"8"))
+            self.assertIsNotNone(re.match((r"\x%02x" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"\x%02x0" % i).encode(), bytes([i])+b"0"))
+            self.assertIsNotNone(re.match((r"\x%02xz" % i).encode(), bytes([i])+b"z"))
+        self.assertIsNotNone(re.match(br"\u", b'u'))
+        self.assertIsNotNone(re.match(br"\U", b'U'))
+        self.assertIsNotNone(re.match(br"\0", b"\000"))
+        self.assertIsNotNone(re.match(br"\08", b"\0008"))
+        self.assertIsNotNone(re.match(br"\01", b"\001"))
+        self.assertIsNotNone(re.match(br"\018", b"\0018"))
+        self.assertIsNotNone(re.match(br"\567", bytes([0o167])))
+        self.assertRaises(re.error, re.match, br"\911", b"")
+        self.assertRaises(re.error, re.match, br"\x1", b"")
+        self.assertRaises(re.error, re.match, br"\x1z", b"")
+
+    def test_sre_byte_class_literals(self):
+        for i in [0, 8, 16, 32, 64, 127, 128, 255]:
+            self.assertIsNotNone(re.match((r"[\%o]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\%o8]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\%03o]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\%03o0]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\%03o8]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\x%02x]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\x%02x0]" % i).encode(), bytes([i])))
+            self.assertIsNotNone(re.match((r"[\x%02xz]" % i).encode(), bytes([i])))
+        self.assertIsNotNone(re.match(br"[\u]", b'u'))
+        self.assertIsNotNone(re.match(br"[\U]", b'U'))
+        self.assertRaises(re.error, re.match, br"[\911]", "")
+        self.assertRaises(re.error, re.match, br"[\x1z]", "")
 
     def test_bug_113254(self):
         self.assertEqual(re.match(r'(a)|(b)', 'b').start(1), -1)
diff --git a/Misc/NEWS b/Misc/NEWS
index 37a0dee..f768602 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -40,6 +40,9 @@
 Library
 -------
 
+- Issue #3665: \u and \U escapes are now supported in unicode regular
+  expressions.  Patch by Serhiy Storchaka.
+
 - Issue #15153: Added inspect.getgeneratorlocals to simplify white box
   testing of generator state updates