Macclenny is a city in Baker County, Florida . Located just west of Jacksonville, it is one of the principal municipalities comprising Greater Jacksonville. The population was 7,304 at the 2020 census, up from 6,374 in 2010. It is the county seat of Baker County.

Macclenny was first called Darbyville because most of the land of this area was owned by the Darby family. Carr Bowers McClenny married into the Darby family, and then bought most of this land in the late 19th century, intending to harvest it for timber.

Darbyville became known as McClenny. McClenny developed many businesses there related to lumber: harvesting the wood, sawmills to process it, turpentine, and land. The town name McClenny was changed to the current name of The City of Macclenny because the post office department had a rule against using capital letters in the middle of a name. The first post office in Macclenny was established in 1890.

There were settlers in Macclenny as early as 1829, but it was not until after the Civil War that more people began to settle there. In 1888 most of the town residents were killed in a yellow fever epidemic. The population was 334 in 1890 (see census table below). The town gradually recovered.

By 2000, residents increased to 4,500. The 2016 population was estimated at 6,562.