The Atrato River is a river of northwestern Colombia. It rises in the slopes of the Western Cordillera and flows almost due north to the Gulf of Urabá (or Gulf of Darién), where it forms a large, swampydelta. Its course crosses the department of Chocó, forming that department's border with neighbouring Antioquia on two occasions. Its total length is about , and it is navigable as far as Quibdó (400 km / 250 mi).