diff --git a/src/hyperlink/_url.py b/src/hyperlink/_url.py
index 8797b5c..e613167 100644
--- a/src/hyperlink/_url.py
+++ b/src/hyperlink/_url.py
@@ -1667,11 +1667,16 @@ def to_uri(self):
         new_path = _encode_path_parts(
             self.path, has_scheme=bool(self.scheme), rooted=False, maximal=True
         )
-        new_host = (
-            self.host
-            if not self.host
-            else idna_encode(self.host, uts46=True).decode("ascii")
-        )
+        # IP literals must not be IDNA-encoded (colons fail idna).
+        if not self.host:
+            new_host = self.host
+        else:
+            family, _ = parse_host(self.host)
+            new_host = (
+                self.host
+                if family is not None
+                else idna_encode(self.host, uts46=True).decode("ascii")
+            )
         return self.replace(
             userinfo=new_userinfo,
             host=new_host,
diff --git a/src/hyperlink/test/test_url.py b/src/hyperlink/test/test_url.py
index 37c9172..b912b1a 100644
--- a/src/hyperlink/test/test_url.py
+++ b/src/hyperlink/test/test_url.py
@@ -1132,6 +1132,15 @@ def test_idna(self):
         self.assertEqual(u2.to_text(), "https://xn--bcher-kva.ch")
         self.assertEqual(u2.to_iri().to_text(), "https://bücher.ch")
 
+    def test_to_uri_ip_literal(self):
+        # type: () -> None
+        ipv6 = URL.from_text("http://[::1]/")
+        self.assertEqual(ipv6.to_uri().to_text(), "http://[::1]/")
+        self.assertEqual(ipv6.to_uri().host, "::1")
+        ipv4 = URL.from_text("http://127.0.0.1/")
+        self.assertEqual(ipv4.to_uri().to_text(), "http://127.0.0.1/")
+        self.assertEqual(ipv4.to_uri().host, "127.0.0.1")
+
     def test_netloc_slashes(self):
         # type: () -> None