Macclenny is a city in Baker County, Florida, United States. The population was 4,459 at the 2000 census. It is the county seat of Baker County. As of 2010, the population recorded by the U.S. Census Bureau is 6,374. The small city of Macclenny has been described by locals as a small, Southern community. The city of Macclenny has some churches as old as 125 years.