Wessel Islands, chain of small islands extending 75 miles (120 km) northeast from the Napier Peninsula in northeastern Northern Territory, Australia, into the Arafura Sea. Named for a Dutch ship that explored the area in 1636, the islands form the western gate to the Gulf of Carpentaria at Cape Wessel, their northern extremity. Marchinbar, the largest island (30 miles by 7 miles [48 km by 11 km]), has undeveloped bauxite deposits. The island group lies within the Arnhem Land Aboriginal Reserve, and the islands have caves decorated with Aboriginal art.