Winn Parish is a parish located in the U.S. state of Louisiana. As of the 2020 census, the population was 13,755. The parish seat and largest city is Winnfield. The parish was founded in 1852. It is last in alphabetical order of Louisiana's sixty-four parishes. Winn is separated from Natchitoches Parish along U.S. Highway 71 by Saline Bayou, the first blackwater protected waterway in the American South.