St. Martinville is a city in, and the parish seat of, St. Martin Parish, Louisiana, United States. It lies on Bayou Teche, 13 miles south of Breaux Bridge, 16 miles southeast of Lafayette, and 9 miles 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.