Delias mysis, the Union Jack or red-banded Jezebel, is a butterfly in the family Pieridae.

It is endemic to northern Australia, New Guinea and neighbouring islands.

The butterfly was given this name, because the patterns and colours on the underside of the wings of the males resembles the flag.

The species has a wide variety in colours and patterns, hence a great deal of subspecies have been named.

The larvae feed on mistletoe species, especially Dendrophthoe glabrescens.