diff --git a/Doc/library/urllib.parse.rst b/Doc/library/urllib.parse.rst
index ef48addaba03e9..24b2ed47d43485 100644
--- a/Doc/library/urllib.parse.rst
+++ b/Doc/library/urllib.parse.rst
@@ -220,6 +220,11 @@ or on combining URL components into a URL string.
    .. versionchanged:: 3.15
       Added the *missing_as_none* parameter.
 
+   .. versionchanged:: 3.15
+      Values for ``url`` and ``scheme`` other than strings, bytes, or ``None``
+      raise :exc:`TypeError` if true or :exc:`DeprecationWarning` if false (to
+      be changed to :exc:`TypeError` in future versions of Python).
+
 .. _WHATWG spec: https://url.spec.whatwg.org/#concept-basic-url-parser
 
 
@@ -315,6 +320,11 @@ or on combining URL components into a URL string.
       query parameter separator. This has been changed to allow only a single
       separator key, with ``&`` as the default separator.
 
+   .. versionchanged:: 3.15
+      Values for ``qs`` and ``separator`` other than strings, bytes, or
+      ``None`` raise :exc:`TypeError` if true or :exc:`DeprecationWarning` if
+      false (to be changed to :exc:`TypeError` in future versions of Python).
+
 
 .. function:: urlunsplit(parts)
               urlunsplit(parts, *, keep_empty)
@@ -374,6 +384,11 @@ or on combining URL components into a URL string.
    .. versionchanged:: 3.15
       Added the *keep_empty* parameter.
 
+   .. versionchanged:: 3.15
+      Items in ``parts`` other than strings, bytes, or ``None`` raise
+      :exc:`TypeError` if true or :exc:`DeprecationWarning` if false (to be
+      changed to :exc:`TypeError` in future versions of Python).
+
 
 .. function:: urljoin(base, url, allow_fragments=True)
 
@@ -417,6 +432,11 @@ or on combining URL components into a URL string.
 
       Behavior updated to match the semantics defined in :rfc:`3986`.
 
+   .. versionchanged:: 3.15
+      Values for ``base`` and ``url`` other than strings, bytes, or ``None``
+      raise :exc:`TypeError` if true or :exc:`DeprecationWarning` if false (to
+      be changed to :exc:`TypeError` in future versions of Python).
+
 
 .. function:: urldefrag(url, *, missing_as_none=False)
 
@@ -447,6 +467,11 @@ or on combining URL components into a URL string.
    .. versionchanged:: 3.15
       Added the *missing_as_none* parameter.
 
+   .. versionchanged:: 3.15
+      Values other than other than strings, bytes, or ``None`` raise
+      :exc:`TypeError` if true or :exc:`DeprecationWarning` if false (to be
+      changed to :exc:`TypeError` in future versions of Python).
+
 .. function:: unwrap(url)
 
    Extract the url from a wrapped URL (that is, a string formatted as
diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst
index c4dac339be66af..f67c6220a5d6b6 100644
--- a/Doc/whatsnew/3.15.rst
+++ b/Doc/whatsnew/3.15.rst
@@ -1761,6 +1761,13 @@ New deprecations
     :func:`issubclass`, but warnings were not previously emitted if it was
     merely imported or accessed from the :mod:`!typing` module.
 
+* :mod:`urllib`:
+
+  * Providing anything but a string, bytes object, or ``None`` to
+    :mod:`urllib.parse` functions expecting strings or bytes now raises
+    :exc:`DeprecationWarning` if the value tests false, or :exc:`TypeError` if
+    it tests true.
+    (Contributed by Jacob Walls in :issue:`19094`.)
 
 * ``__version__``
 
diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py
index 8e4da0e0f09919..ff5cf70ee30470 100644
--- a/Lib/test/test_urlparse.py
+++ b/Lib/test/test_urlparse.py
@@ -1255,7 +1255,14 @@ def test_mixed_types_rejected(self):
         with self.assertRaisesRegex(TypeError, "Cannot mix str"):
             urllib.parse.urljoin(b"http://python.org", "http://python.org")
 
+    def test_non_string_true_values_rejected(self):
+        # True values raise informative TypeErrors
+        msg = "Expected a string, bytes, or None: got <class "
+        with self.assertRaisesRegex(TypeError, msg):
+            urllib.parse.urlsplit(1, b'http')
+
     def _check_result_type(self, str_type, str_args):
+        num_args = len(str_type._fields)
         bytes_type = str_type._encoded_counterpart
         self.assertIs(bytes_type._decoded_counterpart, str_type)
         bytes_args = tuple_encode(str_args)
@@ -1987,6 +1994,23 @@ def test_to_bytes_deprecation(self):
         self.assertEqual(str(cm.warning),
                          'urllib.parse.to_bytes() is deprecated as of 3.8')
 
+    def test_falsey_deprecation(self):
+        cases = [
+            (urllib.parse.urljoin, ['http://www.python.org', []]),
+            (urllib.parse.urljoin, [[], b'docs']),
+            (urllib.parse.urlparse, [b'www.python.org', {}]),
+            (urllib.parse.urlparse, [{}, '']),
+            (urllib.parse.urlsplit, [0, b'http']),
+            (urllib.parse.urlsplit, [b'http://www.python.org', 0]),
+            (urllib.parse.urldefrag, [{}]),
+            (urllib.parse.urlunparse, [[None, b'www.python.org', (), (), (), ()]]),
+            (urllib.parse.urlunsplit, [['http', 0, '', '', '']]),
+        ]
+        for callable, args in cases:
+            with self.subTest(callable=callable.__name__, args=args):
+                with self.assertWarnsRegex(DeprecationWarning, "false values"):
+                    callable(*args)
+
 
 def str_encode(s):
     if s is None:
diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
index d64f678d235b6f..b1d442e4778aca 100644
--- a/Lib/urllib/parse.py
+++ b/Lib/urllib/parse.py
@@ -124,6 +124,7 @@ def _coerce_args(*args):
     #   - noop for str inputs
     #   - encoding function otherwise
     str_input = None
+    empty_values = {"", b"", None}
     for arg in args:
         if arg:
             if str_input is None:
@@ -131,6 +132,13 @@ def _coerce_args(*args):
             else:
                 if isinstance(arg, str) != str_input:
                     raise TypeError("Cannot mix str and non-str arguments")
+            if arg is not None and str_input is False and not hasattr(arg, "decode"):
+                raise TypeError(f"Expected a string, bytes, or None: got {type(arg)}")
+        elif arg is not None and not isinstance(arg, str) and not hasattr(arg, "decode"):
+            warnings.warn(
+                f"Providing false values other than empty strings, bytes, or"
+                f"None to urllib.parse is deprecated: got {type(arg)}",
+                DeprecationWarning, stacklevel=3)
     if str_input is None:
         for arg in args:
             if arg is not None:
@@ -697,12 +705,12 @@ def _urlunsplit(scheme, netloc, url, query, fragment):
 def urljoin(base, url, allow_fragments=True):
     """Join a base URL and a possibly relative URL to form an absolute
     interpretation of the latter."""
+    base, url, _coerce_result = _coerce_args(base, url)
     if not base:
-        return url
+        return _coerce_result(url)
     if not url:
-        return base
+        return _coerce_result(base)
 
-    base, url, _coerce_result = _coerce_args(base, url)
     bscheme, bnetloc, bpath, bquery, bfragment = \
             _urlsplit(base, None, allow_fragments)
     scheme, netloc, path, query, fragment = \
diff --git a/Misc/NEWS.d/next/Library/2021-06-11-20-00-16.bpo-19094.rMRoIL.rst b/Misc/NEWS.d/next/Library/2021-06-11-20-00-16.bpo-19094.rMRoIL.rst
new file mode 100644
index 00000000000000..51c864b91a5fe0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2021-06-11-20-00-16.bpo-19094.rMRoIL.rst
@@ -0,0 +1,3 @@
+Providing anything but a string or bytes object to :mod:`urllib.parse`
+functions expecting strings or bytes now raises :exc:`DeprecationWarning`
+if the value tests false, or :exc:`TypeError` if it tests true.