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. It is connected to the Vistula by the river Noteć and the Bydgoszcz Canal (Kanał Bydgoski) near Bydgoszcz.
The Greater Polish Warta river basin was the original Poland —it is said that the Polans (Polish: Polanie), a West Slavic tribe, inhabited the Warta river basin from the 8th century. The river is also mentioned in the second stanza of the Mazurek Dąbrowskiego Polish national anthem.