diff -r ea401e7c55e4 Lib/test/test_urlparse.py
--- a/Lib/test/test_urlparse.py	Thu Sep 18 21:37:26 2014 +0800
+++ b/Lib/test/test_urlparse.py	Thu Sep 18 07:49:33 2014 -0700
@@ -380,6 +380,19 @@
         # self.checkJoin(SIMPLE_BASE, '../../../g','http://a/../g')
         # self.checkJoin(SIMPLE_BASE, '/./g','http://a/./g')
 
+        # test for issue22118 duplicate slashes
+        self.checkJoin(SIMPLE_BASE + '/', 'foo', SIMPLE_BASE + '/foo')
+
+        # Non-RFC-specific tests, covering variations of base and
+        # Non-RFC-defined tests, covering variations of base and trailing
+        # slashes
+        self.checkJoin('http://a/b/c/d/e/', '../../f/g/', 'http://a/b/c/f/g/')
+        self.checkJoin('http://a/b/c/d/e', '../../f/g/', 'http://a/b/f/g/')
+        self.checkJoin('http://a/b/c/d/e/', '/../../f/g/', 'http://a/f/g/')
+        self.checkJoin('http://a/b/c/d/e', '/../../f/g/', 'http://a/f/g/')
+        self.checkJoin('http://a/b/c/d/e/', '../../f/g', 'http://a/b/c/f/g')
+        self.checkJoin('http://a/b/', '../../f/g/', 'http://a/f/g/')
+
     def test_RFC2732(self):
         str_cases = [
             ('http://Test.python.org:5432/foo/', 'test.python.org', 5432),
diff -r ea401e7c55e4 Lib/urllib/parse.py
--- a/Lib/urllib/parse.py	Thu Sep 18 21:37:26 2014 +0800
+++ b/Lib/urllib/parse.py	Thu Sep 18 07:49:33 2014 -0700
@@ -443,10 +443,14 @@
         segments = path.split('/')
     else:
         segments = base_parts + path.split('/')
+        # filter out elements that would cause redundant slashes on re-joining
+        # the resolved_path
+        segments = segments[0:1] + [
+            s for s in segments[1:-1] if len(s) > 0] + segments[-1:]
 
     resolved_path = []
 
-    for seg in segments:
+    for idx, seg in enumerate(segments):
         if seg == '..':
             try:
                 resolved_path.pop()
@@ -465,7 +469,7 @@
         resolved_path.append('')
 
     return _coerce_result(urlunparse((scheme, netloc, '/'.join(
-        resolved_path), params, query, fragment)))
+        resolved_path) or '/', params, query, fragment)))
 
 
 def urldefrag(url):