Long Key State Park, State park in Monroe County, United States.

Long Key State Park covers 965 acres on Long Key, at mile marker 67.5 of the Overseas Highway. The island lies barely above sea level, with low seagrass flats, about 56 hectares of shallow lagoons, and higher wooded hammocks. A line of rough gray rocks separates the grass from the sandy shore.

Long Key became a depot on Henry Flagler's Key West Extension of the Florida East Coast Railroad, and Flagler also set up the Long Key Fishing Camp there, drawing saltwater anglers from around the world. The Labor Day Hurricane of 1935 destroyed the camp, the railroad and much of the Keys. The park's land was acquired between 1961 and 1973, and the state park opened officially on 1 October 1969.

Spanish explorers named the island "Cayo Vivora", or Rattlesnake Key, for its shape, which to them looked like a snake with open jaws. The name Long Key later replaced it. Visitors today see the low island and its shoreline that prompted the comparison.

The park is located at mile marker 67.5 on the Overseas Highway and offers 60 camping sites, two nature trails, kayak rentals, and swimming areas. Visitors should prepare for flat terrain and potential heat, as shade is limited throughout the grounds.

The Golden Orb Trail is named after a native spider and runs about 3 km in total with the Layton Trail; a boardwalk leads to a wooden observation tower with a panoramic view of the island. The Layton Trail ends at the shore of Florida Bay.