diff --git a/news/6795.bugfix b/news/6795.bugfix
new file mode 100644
index 00000000000..f80bd9b4b2f
--- /dev/null
+++ b/news/6795.bugfix
@@ -0,0 +1 @@
+ Fix handling of tokens (single part credentials) in URLs.
diff --git a/src/pip/_internal/download.py b/src/pip/_internal/download.py
index 1578521c765..d5c57ee0395 100644
--- a/src/pip/_internal/download.py
+++ b/src/pip/_internal/download.py
@@ -307,7 +307,7 @@ def _get_new_credentials(self, original_url, allow_netrc=True,
                 logger.debug("Found credentials in keyring for %s", netloc)
                 return kr_auth
 
-        return None, None
+        return username, password
 
     def _get_url_and_credentials(self, original_url):
         """Return the credentials to use for the provided URL.
@@ -324,15 +324,29 @@ def _get_url_and_credentials(self, original_url):
         # Use any stored credentials that we have for this netloc
         username, password = self.passwords.get(netloc, (None, None))
 
-        # If nothing cached, acquire new credentials without prompting
-        # the user (e.g. from netrc, keyring, or similar).
-        if username is None or password is None:
+        if username is None and password is None:
+            # No stored credentials. Acquire new credentials without prompting
+            # the user. (e.g. from netrc, keyring, or the URL itself)
             username, password = self._get_new_credentials(original_url)
 
-        if username is not None and password is not None:
-            # Store the username and password
+        if username is not None or password is not None:
+            # Convert the username and password if they're None, so that
+            # this netloc will show up as "cached" in the conditional above.
+            # Further, HTTPBasicAuth doesn't accept None, so it makes sense to
+            # cache the value that is going to be used.
+            username = username or ""
+            password = password or ""
+
+            # Store any acquired credentials.
             self.passwords[netloc] = (username, password)
 
+        assert (
+            # Credentials were found
+            (username is not None and password is not None) or
+            # Credentials were not found
+            (username is None and password is None)
+        ), "Could not load credentials from url: {}".format(original_url)
+
         return url, username, password
 
     def __call__(self, req):
diff --git a/tests/unit/test_download.py b/tests/unit/test_download.py
index d63d7420178..42918c20e75 100644
--- a/tests/unit/test_download.py
+++ b/tests/unit/test_download.py
@@ -490,18 +490,53 @@ def test_insecure_host_cache_is_not_enabled(self, tmpdir):
         assert not hasattr(session.adapters["https://example.com/"], "cache")
 
 
-def test_get_credentials():
+@pytest.mark.parametrize(["input_url", "url", "username", "password"], [
+    (
+        "http://user%40email.com:password@example.com/path",
+        "http://example.com/path",
+        "user@email.com",
+        "password",
+    ),
+    (
+        "http://username:password@example.com/path",
+        "http://example.com/path",
+        "username",
+        "password",
+    ),
+    (
+        "http://token@example.com/path",
+        "http://example.com/path",
+        "token",
+        "",
+    ),
+    (
+        "http://example.com/path",
+        "http://example.com/path",
+        None,
+        None,
+    ),
+])
+def test_get_credentials_parses_correctly(input_url, url, username, password):
     auth = MultiDomainBasicAuth()
     get = auth._get_url_and_credentials
 
     # Check URL parsing
-    assert get("http://foo:bar@example.com/path") \
-        == ('http://example.com/path', 'foo', 'bar')
-    assert auth.passwords['example.com'] == ('foo', 'bar')
+    assert get(input_url) == (url, username, password)
+    assert (
+        # There are no credentials in the URL
+        (username is None and password is None) or
+        # Credentials were found and "cached" appropriately
+        auth.passwords['example.com'] == (username, password)
+    )
+
 
+def test_get_credentials_uses_cached_credentials():
+    auth = MultiDomainBasicAuth()
     auth.passwords['example.com'] = ('user', 'pass')
-    assert get("http://foo:bar@example.com/path") \
-        == ('http://example.com/path', 'user', 'pass')
+
+    got = auth._get_url_and_credentials("http://foo:bar@example.com/path")
+    expected = ('http://example.com/path', 'user', 'pass')
+    assert got == expected
 
 
 def test_get_index_url_credentials():