Flat Island may refer to:
Flat Island (Antarctica), in Robertson Bay Flat Island (Hong Kong) Flat Island (Spratly) in the South China Sea Flat Island (Falkland Islands) in the south Atlantic Ocean Flat Island Wildlife Sanctuary, in the Andaman Islands Flat Island, a former separate island now merged by recent volcanic activity with McDonald Island, in the southern Indian Ocean Flat Island, one of the Engineer Islands in southeast Papua New Guinea Île Plate, also known as Flat Island, a small island off the north coast of Mauritius Sandy Point, Newfoundland and Labrador
See also Flat Islands (disambiguation) Flat Isles Flat Islet, Queensland