St. Martin Parish is a parish located in the U.S. state of Louisiana, founded in 1811. Its parish seat is St. Martinville, and the largest city is Breaux Bridge. At the 2020 census, the population was 51,767. St. Martin Parish is part of the Lafayette metropolitan area in the region of Acadiana, along the Gulf Coast.

St. Martinville is a city in and the parish seat of St. Martin Parish, Louisiana, United States. It lies on Bayou Teche, 13 miles (21 km) south of Breaux Bridge, 16 miles (26 km) southeast of Lafayette, and 9 miles (14 km) north of New Iberia. The population was 6,114 at the 2010 U.S. census, and 5,379 at the 2020 United States census. It is part of the Lafayette metropolitan statistical area.