Port Sulphur is a census-designated place (CDP) on the West Bank of the Mississippi River in Plaquemines Parish, Louisiana, United States. The population was 3,115 at the 2000 census. The name Port Sulphur derives from the Freeport Sulfur Company in the early 1900s, when it set up drilling, refinery and shipping operations. The site is valuable because of its proximity to the Gulf of Mexico, its docking site along the Mississippi River and the surrounding natural resources.