The Florida Keys are a coral cay archipelago off the southern coast of Florida, forming the southernmost part of the continental United States. They begin at the southeastern coast of the Florida peninsula, about 15 miles (24 km) south of Miami and extend in a gentle arc south-southwest and then westward to Key West, the westernmost of the inhabited islands, and on to the uninhabited Dry Tortugas. The islands lie along the Florida Straits, dividing the Atlantic Ocean to the east from the Gulf of Mexico to the northwest, and defining one edge of Florida Bay. The southern part of Key West is 93 miles (150 km) from Cuba. The Keys are located between about 24.3 and 25.5 degrees North latitude.

A cay, also spelled caye or key, is a small, low-elevation, sandy island on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic, and Indian oceans, including in the Caribbean and on the Great Barrier Reef and Belize Barrier Reef.