---
 Lib/test/test_urlparse.py                                             |   20 ++++++++++
 Lib/urlparse.py                                                       |    2 -
 Misc/NEWS.d/next/Library/2022-11-12-15-45-51.gh-issue-99418.FxfAXS.rs |    2 +
 3 files changed, 23 insertions(+), 1 deletion(-)

--- a/Lib/test/test_urlparse.py
+++ b/Lib/test/test_urlparse.py
@@ -592,6 +592,26 @@ class UrlParseTestCase(unittest.TestCase
         self.assertEqual(p.netloc, "www.example.net:foo")
         self.assertRaises(ValueError, lambda: p.port)
 
+    def do_attributes_bad_scheme(self, bytes, parse, scheme):
+        url = scheme + "://www.example.net"
+        if bytes:
+            if url.isascii():
+                url = url.encode("ascii")
+            else:
+                continue
+        p = parse(url)
+        if bytes:
+            self.assertEqual(p.scheme, b"")
+        else:
+            self.assertEqual(p.scheme, "")
+
+    def test_attributes_bad_scheme(self):
+        """Check handling of invalid schemes."""
+        for bytes in (False, True):
+            for parse in (urlparse.urlsplit, urlparse.urlparse):
+                for scheme in (".", "+", "-", "0", "http&", "६http"):
+                    self.do_attributes_bad_scheme(bytes, parse, scheme)
+
     def test_attributes_without_netloc(self):
         # This example is straight from RFC 3261.  It looks like it
         # should allow the username, hostname, and port to be filled
--- a/Lib/urlparse.py
+++ b/Lib/urlparse.py
@@ -211,7 +211,7 @@ def urlsplit(url, scheme='', allow_fragm
         clear_cache()
     netloc = query = fragment = ''
     i = url.find(':')
-    if i > 0:
+    if i > 0 and url[0].isascii() and url[0].isalpha():
         if url[:i] == 'http': # optimize the common case
             scheme = url[:i].lower()
             url = url[i+1:]
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-11-12-15-45-51.gh-issue-99418.FxfAXS.rs
@@ -0,0 +1,2 @@
+Fix bug in :func:`urllib.parse.urlparse` that causes URL schemes that begin
+with a digit, a plus sign, or a minus sign to be parsed incorrectly.