diff --git a/src/hyperlink/_url.py b/src/hyperlink/_url.py
index 8797b5c..ff69aa5 100644
--- a/src/hyperlink/_url.py
+++ b/src/hyperlink/_url.py
@@ -1035,6 +1035,8 @@ def __init__(
         )
         self._fragment = _textcheck("fragment", fragment)
         self._port = _typecheck("port", port, int, NoneType)
+        if self._port is not None and not (0 <= self._port <= 65535):
+            raise ValueError("port must be in range 0-65535, not %r" % (self._port,))
         self._rooted = _typecheck("rooted", rooted, bool)
         self._userinfo = _textcheck("userinfo", userinfo, "/?#@")
 
@@ -1413,6 +1415,10 @@ def from_text(cls, text):
                 if not port:  # TODO: excessive?
                     raise URLParseError("port must not be empty: %r" % au_text)
                 raise URLParseError("expected integer for port, not %r" % port)
+            if not (0 <= port <= 65535):
+                raise URLParseError(
+                    "port must be in range 0-65535, not %r" % (port,)
+                )
 
         scheme = gs["scheme"] or u""
         fragment = gs["fragment"] or u""
diff --git a/src/hyperlink/test/test_url.py b/src/hyperlink/test/test_url.py
index 37c9172..7ea1517 100644
--- a/src/hyperlink/test/test_url.py
+++ b/src/hyperlink/test/test_url.py
@@ -1493,3 +1493,25 @@ def test_idna_corners(self):
         assert (
             URL.from_text(text).to_uri().get_decoded_url().host == "example.com"
         )
+
+
+class OutOfRangePortTests(HyperlinkTestCase):
+    def test_from_text_rejects_out_of_range_port(self):
+        from hyperlink import URL, URLParseError
+        for bad in ("http://ex.com:-1", "http://ex.com:65536", "http://ex.com:99999"):
+            try:
+                URL.from_text(bad)
+            except URLParseError:
+                pass
+            else:
+                raise AssertionError("expected URLParseError for %r" % (bad,))
+
+    def test_ctor_rejects_out_of_range_port(self):
+        from hyperlink import URL
+        for bad in (-1, 65536, 99999):
+            try:
+                URL(scheme=u"http", host=u"ex.com", port=bad)
+            except ValueError:
+                pass
+            else:
+                raise AssertionError("expected ValueError for port %r" % (bad,))