Natchitoches is a city in and the parish seat of Natchitoches Parish, Louisiana, United States. The population was 18,039 at the 2020 census. Established in 1714 by Louis Juchereau de St. Denis as part of French Louisiana, the community was named after the indigenous Natchitoches people. The city was incorporated on February 5, 1819, and is the oldest permanent settlement in the land acquired by the Louisiana Purchase. Natchitoches is home to Northwestern State University of Louisiana. Its sister city is Nacogdoches, Texas.