The Warta (Polish pronunciation: [ˈvaɾta] German: Warthe; Latin: Varta) is a river in western-central Poland, a tributary of the Oder river. With a length of approximately 808 kilometres (502 mi) it is the country's third longest river. The Warta has a basin area of 54,529 square kilometers, and it is navigable from Kostrzyn nad Odrą to Konin, approximately half of its length.