Bayou Queue de Tortue (pronounced "KYOOD tor-TYOO", translated to "turtle-tail bayou") is a waterway in the Mermentau River basin of southern Louisiana in the United States. The bayou is 55 miles (89 km) long and is partly navigable. The bayou begins near Lafayette and forms the natural boundary separating Lafayette Parish and Acadia Parish to the west and Acadia Parish and Vermilion Parish to the south.