Jonesville is the largest town in Catahoula Parish, Louisiana, United States, at the confluence of the Ouachita, Tensas, and Little rivers. The three rivers become the Black River at Jonesville.

Catahoula Parish is a parish in the U.S. state of Louisiana. As of the 2020 census, the population was 8,906. Its seat is Harrisonburg, on the Ouachita River. The parish was formed in 1808, shortly after the United States acquired this territory in the Louisiana Purchase of 1803.