The Vermilion River (or the Bayou Vermilion) is a  river in southern Louisiana in the United States. It is formed on the common boundary of Lafayette and St. Martin parishes by a confluence of small bayous flowing from St. Landry Parish, and flows generally southward through Lafayette and Vermilion parishes, past the cities of Lafayette and Abbeville. At the port of Intracoastal City, the Gulf Intracoastal Waterway crosses the river before the latter flows into Vermilion Bay, an inlet of the Gulf of Mexico. The river originates at Bayou Fusilier, which is fed by Bayou Teche; winds its way through Lafayette Parish; and drains into the Vermilion Bay below Vermilion Parish.