Mornington Island, also known as Kunhanhaa, is an island in the Gulf of Carpentaria in the Shire of Mornington, Queensland, Australia. It is the northernmost and largest of 22 islands that form the Wellesley Islands group. The largest town, Gununa, is in the south-western part of the island.

The Shire of Mornington is a local government area in northwestern Queensland, Australia. The shire covers the Wellesley Islands, which includes Mornington Island; the South Wellesley Islands; Bountiful Islands; and West Wellesley / Forsyth Islands groups in the Gulf of Carpentaria.