Southwest Pass is a narrow strait in southern Louisiana connecting the Gulf of Mexico with Vermilion Bay. Located in Vermilion Parish, it is bounded by Marsh Island on the east and the mainland of southeastern Vermilion Parish on the west. As part of the region’s low, marshy coastal landscape, it forms a natural link between open Gulf waters and the bay inland. Although its name is often confused with the better-known Southwest Pass at the mouth of the Mississippi River, this is a distinct waterway with its own place along the Vermilion Bay shore.