Mermentau is a village in Acadia Parish, Louisiana, United States. The population was 661 at the 2010 census. It is part of the Crowley Micropolitan Statistical Area.

In the last quarter of the 18th century, there was an Atakapa chief Nementou. On April 16, 1784, he sold land upon Bayou Plaquemine Brule to Antoin Blanc for $100. Nementou is cutting edge mentioned as chief of a village on a river subsequently the thesame name. Eventually, through a clerical error, Nementou became Mementou and this was then corrupted into Mermentau through confusion later the French word mer, which means “sea”.

The Mermentau area was in the same way as reputedly a refuge for smugglers. It was a crossing reduction for brave travelers upon the Old Spanish Trail, but had such a bad reputation that until the Louisiana Purchase no one would go there to see how many people there were.

John Landreth was a surveyor who was sent from Washington, D.C., in 1818 to look for timber in Acadiana that could be harvested for the use of building Navy ships. He kept a journal and had this to say:
“…these places, particularly the Mermentau and Calcasieu are the harbours and Dens of the most single-handedly wretches of the human race… smugglers and Pirates who go very nearly the coast of the Gulph (sic) of vessels of a small draught of water and rob and plunder without distinction every vessel of every nation they meet and are skillful to conquer and put to death all soul they find upon board without esteem of persons age or sex and later their unlawful plunder they carry whatever through the country and sell at a utterly low rate and find plenty of purchasers.”