diff --git a/src/gleam/uri.gleam b/src/gleam/uri.gleam
index cc0c3ac7..652e28a5 100644
--- a/src/gleam/uri.gleam
+++ b/src/gleam/uri.gleam
@@ -202,7 +202,7 @@ fn parse_host(uri_string: String, pieces: Uri) -> Result(Uri, Nil) {
   // - [^:]
   case uri_string {
     // If we find an opening bracket we know it's the first format.
-    "[" <> _ -> parse_host_within_brackets(uri_string, pieces)
+    "[" <> rest -> parse_host_within_brackets(rest, pieces)
 
     // A `:` marks the beginning of the port part of the authority string.
     ":" <> _ -> {
@@ -233,66 +233,38 @@ fn parse_host_within_brackets_loop(
   size: Int,
 ) -> Result(Uri, Nil) {
   case uri_string {
-    // If the string is over the entire string we were iterating through is the
-    // host part.
-    "" -> Ok(Uri(..pieces, host: Some(uri_string)))
+    // We reached the end without finding a closing `]`.
+    "" -> Error(Nil)
 
     // A `]` marks the end of the host and the start of the port part.
-    "]" <> rest if size == 0 -> parse_port(rest, pieces)
+    "]" <> _ if size == 0 -> Error(Nil)
     "]" <> rest -> {
-      let host = codeunit_slice(original, at_index: 0, length: size + 1)
+      let host = "[" <> codeunit_slice(original, at_index: 0, length: size + 1)
       let pieces = Uri(..pieces, host: Some(host))
       parse_port(rest, pieces)
     }
-
-    // `/` marks the beginning of a path.
-    "/" <> _ if size == 0 -> parse_path(uri_string, pieces)
-    "/" <> _ -> {
-      let host = codeunit_slice(original, at_index: 0, length: size)
-      let pieces = Uri(..pieces, host: Some(host))
-      parse_path(uri_string, pieces)
-    }
-
-    // `?` marks the beginning of the query with question mark.
-    "?" <> rest if size == 0 -> parse_query_with_question_mark(rest, pieces)
-    "?" <> rest -> {
-      let host = codeunit_slice(original, at_index: 0, length: size)
-      let pieces = Uri(..pieces, host: Some(host))
-      parse_query_with_question_mark(rest, pieces)
-    }
-
-    // `#` marks the beginning of the fragment part.
-    "#" <> rest if size == 0 -> parse_fragment(rest, pieces)
-    "#" <> rest -> {
-      let host = codeunit_slice(original, at_index: 0, length: size)
-      let pieces = Uri(..pieces, host: Some(host))
-      parse_fragment(rest, pieces)
-    }
-
     // In all other cases we just keep iterating.
     _ -> {
       let #(char, rest) = pop_codeunit(uri_string)
-      // Inside `[...]` there can only be some characters, if we find a special
-      // one then we know that we're actually parsing the other format for the
-      // host and we switch to that!
+      // Inside `[...]` there can only be some characters.
       case is_valid_host_within_brackets_char(char) {
         True ->
           parse_host_within_brackets_loop(original, rest, pieces, size + 1)
 
-        False ->
-          parse_host_outside_of_brackets_loop(original, original, pieces, 0)
+        False -> Error(Nil)
       }
     }
   }
 }
 
 fn is_valid_host_within_brackets_char(char: Int) -> Bool {
+  // Valid IPv6 hosts are only [0-9A-Fa-f:.].
   // [0-9]
-  { 48 >= char && char <= 57 }
-  // [A-Z]
-  || { 65 >= char && char <= 90 }
-  // [a-z]
-  || { 97 >= char && char <= 122 }
+  { 48 <= char && char <= 57 }
+  // [A-F]
+  || { 65 <= char && char <= 70 }
+  // [a-f]
+  || { 97 <= char && char <= 102 }
   // :
   || char == 58
   // .
diff --git a/src/gleam_stdlib.erl b/src/gleam_stdlib.erl
index d89cb831..660d7178 100644
--- a/src/gleam_stdlib.erl
+++ b/src/gleam_stdlib.erl
@@ -233,7 +233,7 @@ uri_parse(String) ->
             {ok, {uri,
                 maps_get_optional_lowercase(Uri, scheme),
                 maps_get_optional(Uri, userinfo),
-                maps_get_optional(Uri, host),
+                maps_get_optional_host(Uri),
                 Port,
                 maps_get_or(Uri, path, <<>>),
                 maps_get_optional(Uri, query),
@@ -251,6 +251,23 @@ maps_get_optional(Map, Key) ->
     catch _:_ -> none
     end.
 
+maps_get_optional_host(Map) ->
+    try {some, bracket_ipv6_host(maps:get(host, Map))}
+    catch _:_ -> none
+    end.
+
+bracket_ipv6_host(Host) when is_binary(Host) ->
+    case binary:match(Host, <<":">>) of
+        nomatch -> Host;
+        _ ->
+            case Host of
+                <<"[", _/binary>> -> Host;
+                _ -> <<"[", Host/binary, "]">>
+            end
+    end;
+bracket_ipv6_host(Host) ->
+    Host.
+
 maps_get_or(Map, Key, Default) ->
     try maps:get(Key, Map)
     catch _:_ -> Default
diff --git a/test/gleam/uri_test.gleam b/test/gleam/uri_test.gleam
index 7f556f22..9cde4555 100644
--- a/test/gleam/uri_test.gleam
+++ b/test/gleam/uri_test.gleam
@@ -274,6 +274,104 @@ pub fn parse_empty_query_3_test() {
   let assert Some("") = assert_parse("http://example.com/test?").query
 }
 
+pub fn parse_ipv6_host_preserves_brackets_test() {
+  let assert Ok(parsed) =
+    uri.parse("http://[2600:1406:bc00:53::b81e:94c8]/wobble")
+  assert parsed.host == Some("[2600:1406:bc00:53::b81e:94c8]")
+}
+
+pub fn parse_ipv6_host_with_port_preserves_brackets_test() {
+  let assert Ok(parsed) =
+    uri.parse("http://[2600:1406:bc00:53::b81e:94c8]:8080/wobble")
+  assert parsed.host == Some("[2600:1406:bc00:53::b81e:94c8]")
+  assert parsed.port == Some(8080)
+}
+
+pub fn parse_ipv6_host_roundtrip_to_string_test() {
+  let assert Ok(parsed) = uri.parse("http://[2600:1406:bc00:53::b81e:94c8]")
+  assert uri.to_string(parsed) == "http://[2600:1406:bc00:53::b81e:94c8]/"
+}
+
+pub fn parse_ipv6_compact_loopback_preserves_brackets_test() {
+  let assert Ok(parsed) = uri.parse("http://[::1]/wobble")
+  assert parsed.host == Some("[::1]")
+  assert parsed.path == "/wobble"
+}
+
+pub fn parse_ipv6_compact_loopback_with_port_test() {
+  let assert Ok(parsed) = uri.parse("http://[::1]:443/wobble")
+  assert parsed.host == Some("[::1]")
+  assert parsed.port == Some(443)
+}
+
+pub fn parse_ipv6_collapsed_middle_preserves_brackets_test() {
+  let assert Ok(parsed) = uri.parse("http://[2001:db8::2:1]/wobble")
+  assert parsed.host == Some("[2001:db8::2:1]")
+}
+
+pub fn parse_ipv6_collapsed_roundtrip_to_string_test() {
+  let assert Ok(parsed) = uri.parse("http://[2001:db8::2:1]")
+  assert uri.to_string(parsed) == "http://[2001:db8::2:1]/"
+}
+
+pub fn parse_ipv6_host_with_path_query_fragment_test() {
+  let assert Ok(parsed) = uri.parse("http://[2001:db8::2:1]/foo/bar?baz=bif#blah")
+  assert parsed.scheme == Some("http")
+  assert parsed.host == Some("[2001:db8::2:1]")
+  assert parsed.path == "/foo/bar"
+  assert parsed.query == Some("baz=bif")
+  assert parsed.fragment == Some("blah")
+  assert parsed.port == None
+  assert parsed.userinfo == None
+}
+
+pub fn parse_malformed_many_opening_brackets_in_host_test() {
+  assert uri.parse("http://[[[[[[[[[[]/") == Error(Nil)
+}
+
+pub fn parse_malformed_nested_opening_bracket_in_host_test() {
+  assert uri.parse("http://[[::1]/") == Error(Nil)
+}
+
+pub fn parse_malformed_unclosed_bracket_host_test() {
+  assert uri.parse("http://[::1[/") == Error(Nil)
+}
+
+pub fn parse_malformed_question_mark_within_bracket_host_test() {
+  assert uri.parse("http://[::1?bad]/") == Error(Nil)
+}
+
+pub fn parse_malformed_slash_within_bracket_host_test() {
+  assert uri.parse("http://[::1/bad]/") == Error(Nil)
+}
+
+pub fn ipv6_uppercase_test() {
+  // ensure A–F upper case are accepted
+  let assert Ok(parsed) = uri.parse("http://[2001:DB8::1]")
+  assert parsed.host == Some("[2001:DB8::1]")
+  assert uri.to_string(parsed) == "http://[2001:DB8::1]/"
+}
+
+pub fn ipv6_mixedcase_test() {
+  let assert Ok(parsed) = uri.parse("http://[2001:dB8:ABcd::]")
+  assert parsed.host == Some("[2001:dB8:ABcd::]")
+}
+
+pub fn parse_ipv6_with_invalid_char_test() {
+  // 'g' is not a hex digit
+  assert uri.parse("http://[::g]/") == Error(Nil)
+  assert uri.parse("http://[::G]/") == Error(Nil)
+}
+
+pub fn parse_bracket_followed_by_text_error_test() {
+  // characters immediately after closing bracket and before slash should error
+  assert uri.parse("http://[::1]foo") == Error(Nil)
+}
+
+pub fn parse_double_closing_bracket_test() {
+  assert uri.parse("http://[::1]]/") == Error(Nil)
+}
+
 pub fn full_uri_to_string_test() {
   let test_uri =
     uri.Uri(