Tekezē River, river, major tributary of the Atbara River, itself a tributary of the Nile. It rises near Lalībela, Ethiopia, and flows in a deep ravine, north and then west, where it forms part of the border between Ethiopia and Eritrea, to enter Sudan below Om Hajer. It joins the Atbara River 35 miles (55 km) northwest of Gedaref. The Tekezē is 470 miles (756 km) long. Its 70-mile (110-km) course in Sudan is dry for almost nine months of the year, but its upper course is often torrential.