Miami-Dade County (known as Dade County until 1997 and many times referred to as simply Miami or Dade) is a county located in the southeastern part of the state of Florida. The United States Census Bureau estimates that the county population was 2,402,208 in 2006, making it the most populous county in Florida and the eighth-most populous county in the United States. It is also Florida's largest county in terms of land, with over 2,431 square miles. The county's population makes up approximately half of the South Florida metropolitan area population and holds most of the principal cities encompassing South Florida, making it the most important of the three counties that make up the area. The county seat is the city of Miami.

The county is home to 35 incorporated cities and many unincorporated areas. The eastern portion of the county is heavily urbanized with many high rises up the coastline, as well as the location of the county's central business district, Downtown Miami. The western portion of the county consists of the Everglades National Park and is unpopulated. East of the mainland in Biscayne Bay is also Biscayne National Park, making Miami the only metropolitan area in the United States that borders two national parks.

The current county mayor is Carlos Alvarez.