Digul River, river rising on the southern slopes of the Star Mountains in the east-central region of the province of Papua, Indonesia, on the island of New Guinea. The river flows 326 miles (525 km) south and west across a low region of extensive swamps (in the rainy season) to empty into the Arafura Sea immediately north of Yos Sudarso (Dolak, or Frederik Hendrik) Island. The river is navigable as far as the town of Tanahmerah, some 200 miles (320 km) upstream.