Masthead Island is a coral cay located in the southern Great Barrier Reef, 60 kilometres northeast of Gladstone, Queensland. The island is a protected area and forms part of Capricornia Cays National Park. Masthead Island is one of the most undisturbed cays in the national park because human and feral animal impacts have been rare. The cay covers an area of 0.45 square kilometres (0.17 sq mi) and is surrounded by a coral reef that is partially exposed at low-tide.