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.