Donaldsonville (historically French:Lafourche-des-Chitimachas) is a city in and the parish seat of Ascension Parish in south Louisiana, United States, located along the River Road of the west bank of the Mississippi River. The population was 7,436 at the 2010 census, a decrease of more than 150 from the 7,605 tabulation in 2000. Donaldsonville is part of the Baton Rouge Metropolitan Statistical Area.