St. Mary Parish is a parish located in the U.S. state of Louisiana. As of the 2020 census, the population was 49,406. The parish seat is Franklin. The parish was created in 1811.

Franklin is a small city in and the parish seat of St. Mary Parish, Louisiana, United States. The population was 7,660 at the 2010 census. The city is located on Bayou Teche, southeast of the cities of Lafayette, 47 miles (76 km) and New Iberia, 28 miles (45 km), and 22 miles (35 km) northwest of Morgan City. It is part of the Morgan City Micropolitan Statistical Area and the larger Lafayette-Acadiana combined statistical area.