Portage Island is an island in the western part of Bellingham Bay in Whatcom County, Washington, USA. It is separated from the Lummi Peninsula by Portage Bay and from the central part of Lummi Island by Hale Passage, in Whatcom County. Portage Island has a land area of 3.803 km² (1.468 sq mi). There was no resident population as of the 2000 census. The land is owned by Whatcom County and the surrounding tide flats are owned by the Lummi Native American tribe.