Stock Island is a census-designated place and unincorporated community situated in Monroe County, Florida, within the United States. Located on an island of the same name immediately east of Key West, it occupies the portion south of US Highway 1, also known as the Overseas Highway. The highway crosses the key at approximately mile markers four through six, positioning the community as a distinct residential area separate from the more tourist-oriented Key West to the west.

The island's name is attributed to the herds of livestock formerly kept there, though some local historians suggest it may derive from an early settler. The community has evolved from its agricultural roots into a year-round residential hub with a stable population. It remains unincorporated, relying on the Monroe County School District for public education services, including schools in Key West and the College of the Florida Keys located on the island.

The landscape is defined by a mix of residential neighborhoods, marinas, and boat yards that accommodate live-aboard residents. The Key West Golf Club and its residential complex occupy nearly one-quarter of the island on the City of Key West side. The area features specific enclaves for artists and shops, alongside ten marinas offering transient slips, charters, and water sports activities, creating a vibrant waterfront character distinct from the surrounding keys.

Stock Island hosts a thriving artist community and offers diverse culinary options including restaurants, food trucks, a distillery, and two craft breweries. The I Love Stock Island organization promotes local culture through a three-day festival in December featuring a lighted boat parade, tours, and culinary contests, as well as quarterly clean-up days. Visitors can explore the neighborhood to see how locals live, visit the Perry Hotel marina, or attend events at Hogfish Bar & Grill.

As of the 2020 census, the population was 4,722, with a median age of 38.4 years and 100 percent of residents living in urban areas. The economy supports a mix of residential living and maritime services, with access provided via US Highway 1 connecting to Key West and Big Pine Key. The community maintains a year-round population, offering a grounded alternative to the tourist-heavy atmosphere of neighboring Key West.