The Birim River or Ok Birim in the western province of New Guinea is a tributary of the Ok Tedi River, which is in turn a tributary of the north Fly River. The Birim river joins the Ok Tedi river from the west between Ningerum and Bige. The Birim river area is inhabited by the Yonggom tribe. They practise tropical forest Swidden agriculture. About 3,000 people, they speak the Ninggerum language of the Ok group.