The Aquin Plain is a region in southern Haiti.
Aquin Plain is an alluvial plain in the south central part of Tiburon Peninsula, southern Haiti covering 711 square kilometers (275 square miles). It is part of a system of coastal basins throughout southwestern Haiti formed by the littoral zones of the watersheds and largely lies within the commune of Aquin, but stretches into Cavaillon and Saint-Louis, and a minority into the Nippes department. The plain is famous for its rich agriculture, including food production, one of Haiti's best known activities. Large areas are given over to agriculture and thus the sparsely populated plain is the biggest remaining area of alluvial grassland in southwest Haiti. Additionally the plain has arable land, and a few areas of latanier trees and coniferous woodland. Its highest point is found in the northern area of the town of St. Louis at 1,330 meters (4,360 feet) above sea level.