Not to be confused with the Triangle Butterflyfish (C. triangulum) and the Triangulate Butterflyfish (C. trifascialis).

The Eastern Triangle Butterflyfish, Chaetodon baronessa, is a species of butterflyfish (family Chaetodontidae). It is found in the central Indo-West Pacific region from the Cocos-Keeling Islands and Indonesia in the eastern Indian Ocean to Fiji and Tonga, north to southern Japan, south to New Caledonia and New South Wales in Australia.