Union Parish is a parish located in the north central section of the U.S. state of Louisiana. As of the 2020 census, the population was 21,107. The parish seat is Farmerville. The parish was created on March 13, 1839, from a section of Ouachita Parish. Its boundaries have changed four times since then.

Farmerville is a town in and the parish seat of Union Parish, Louisiana, United States. It has also been known as Farmersville. The population was 3,860 at the 2010 census. It is part of the Monroe Metropolitan Statistical Area. The town is spread about Lake D'Arbonne, a popular fishing and boating waterway.