Key Biscayne is an island town in Miami-Dade County, Florida, United States. The population was 14,809 at the 2020 census, up from 12,344 in 2010.

Key Biscayne lies south of Miami Beach and east of Miami. The village is amalgamated to Miami via the Rickenbacker Causeway, originally built in 1947. Because of its low elevation and talk to exposure to the Atlantic Ocean, it is usually in the midst of the first Miami areas to be evacuated previously an oncoming hurricane.

According to the U.S. Census Bureau, the town has a total area of 1.7 square miles (4.4 km). 1.2 square miles (3.1 km²) of it are home and 0.5 square miles (1 km) of it (27.0%) are water. The village is bordered upon the north by Crandon Park, a 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 manufacture a town on Key Biscayne, it wasn’t until the establishment of the 4-mile-long (6.4 km) Rickenbacker Causeway from Miami to Virginia Key and on to Key Biscayne in 1947 that the island was opened in the works 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 relatives donated higher than 800 acres (3.2 km) of their land to Dade County for a public park (Crandon Park) in squabble for a duty that the county would build a causeway to the island. The unshakable Matheson property, stretching across the center of the island, was later sold off to developers. Starting in 1951, the Mackle Construction Company offered extra homes upon the island for US$9,540, with just US$500 down. A U.S. Post Office concurrence branch was opened, the Community Church started holding services in an archaic coconut-husking shed, and the Key Biscayne Elementary School opened in 1952.