Gunnison Island is located in the northwest quadrant of the Great Salt Lake in Box Elder County, Utah, United States, approximately 55 miles northwest of Salt Lake City and about 6 miles east from the lake's western shore. Approximately 1 mile long and 0.5 miles wide, Gunnison Island is best known as an important rookery for the American white pelican. The California gull also nests on the island, and occasional nesters include the great blue heron, common raven, prairie falcon, and rock wren.
The entire island is the Gunnison Island State Wildlife Management Area. Access to the island is restricted to prevent curious tourists from disturbing the nesting birds.
Wildlife biologists estimate that the population on Gunnison Island constitutes about 10–20% of the entire American white pelican population; there are also about 15,000 California gulls that nest on the island.
Historically, the island's remote location protected it from predators, which made it an ideal spot for ground-nesting birds. However, due to recent low lake levels, it is no longer an island; it is connected to shore by a land bridge which predators can use.