Moresby Island is a large island () that forms part of the Queen Charlotte Islands archipelago (also known as Haida Gwaii) in British Columbia, Canada, located at . Gwaii Haanas National Park Reserve and Haida Heritage Site includes Moresby and other islands. The island, together with its numerous nearby smaller islands and islets in the southern portion of the archipelago, is defined by Statistics Canada as Skeena-Queen Charlotte E, with a population was 402 as of the 2006 census. Almost all of its population resided in the unincorporated community of Sandspit, on the northeast corner of Moresby. The total land area of the electoral area is .
Moresby Island is named for Rear Admiral Fairfax Moresby. The traditional name in the Haida language is Gwaii Haanas, which is where the national park name is derived from.