Miami Dade County (formerly known as Dade County) is a county located in the southeastern part of the state of Florida. As of the 2000 U.S. census, the population was 2,253,362, making it the most populated county in the state. The 2005 census estimate indicated a population of 2,376,014, making it the eighth most populous county in the nation. Its county seat is Miami, located in the northeastern part. 51.4% of Miami-Dade County residents are foreign-born, a percentage greater than any other county in the United States. 60.6% of Miami-Dade County residents are Hispanic, 20.5% are black, and only 18.6% are white non-Hispanic.

According to the U.S. Census Bureau, the county has a total area of 6,297 km² (2,431 mi²). 5,040 km² (1,946 mi²) of it is land and 1,257 km² (485 mi²) of it (19.96%) is water, most of which is Biscayne Bay, with another significant portion in the adjacent waters of the Atlantic Ocean. The bay is divided from the Atlantic Ocean by the many barrier isles along the coast, one of which is where well-known Miami Beach is located, home to South Beach and the Art Deco district. The Florida Keys, which are also barrier islands are only accessible through Miami-Dade County, but which are otherwise part of neighboring Monroe County.