Fox Island is an island and census-designated place in Pierce County, Washington, United States, in Puget Sound. It is located approximately 5 miles from Gig Harbor. The island was named Fox by Charles Wilkes during the United States Exploring Expedition, to honor J.L. Fox, an assistant surgeon on the expedition. The population was 3,921 at the 2020 census, up from 3,633 at the 2010 census.