river in Indonesian Irian Jaya, northwestern New Guinea. Formed by the confluence of the Taritatu (Idenburg) and Tariku (Rouffaer) rivers, which converge in a large wild sago swamp, it flows generally northwest and empties into the Pacific Ocean near Tanjung (cape) D'Urville. After flowing placidly the first 20 mi (32 km), the river cuts through the Pegunungan (mountains) Van Rees in a series of rapids and gorges. Including its headstream, the Taritatu, the Mamberamo is about 500 mi long and forms the largest drainage system of Irian Jaya. It is navigable for 100 mi from its mouth, but the only settlements consist of small villages.