Key Biscayne is an island town in Miami-Dade County, Florida, United States. The population was 12,344 at the 2010 census (in July 1, 2019 population was estimated in 12,846).
Key Biscayne lies south of Miami Beach and east of Miami. The village is connected to Miami via the Rickenbacker Causeway, originally built in 1947. Because of its low elevation and direct exposure to the Atlantic Ocean, it is usually among the first Miami areas to be evacuated before an oncoming hurricane.
According to the United States Census Bureau, the town has a total area of 1.4 square miles (3.6 km2). 1.3 square miles (3.4 km2) of it is land and 0.1 square miles (0.26 km2) of it (8.63%) is water.
The village is bordered on the north by Crandon Park, Miami-Dade County park, on the south by Bill Baggs Cape Florida State Park, on the east by the Atlantic Ocean and on the west by Biscayne Bay.
While there had been earlier schemes to develop a town on Key Biscayne, it wasn't until the opening of the four-mile (6 km) long Rickenbacker Causeway from Miami to Virginia Key and on to Key Biscayne in 1947 that the island was opened up to large scale residential development. The northern two-thirds of the island had been operated as the largest coconut plantation in the continental United States during the first half of the 20th century. In 1940 the Matheson family donated over 800 acres (3.2 km2) of their land to Dade County for a public park (Crandon Park) in exchange for a commitment that the county would build a causeway to the island.