Lake Eyasi (Swahili: Ziwa Eyasi; formerly German: Njarasasee, "Njarasa Lake", and Hohenlohesee, "Hohenlohe Lake") is a lake located in Karatu District of Arusha Region in north Tanzania. Lake Eyasi is the largest body of water in Arusha region. It is a seasonal shallow endorheic salt lake on the floor of the Great Rift Valley at the base of the Serengeti Plateau, just south of the Serengeti National Park and immediately southwest of the Ngorongoro Crater in the Crater Highlands of Tanzania. The lake is elongated, orientated southwest to northeast, and lies in the Eyasi-Wembere branch of the Great Rift Valley.
The principal inflow is the Sibiti River, which enters the southwestern end. The river may continue to flow somewhat year round, at least in wetter years; the other inflows are all seasonal. The second largest inflow is the Baray, at the northeast. The water carried by the Baray has increased in recent years due to deforestation of the Crater Highlands. The southwest flank of Mount Oldeani, one of the Ngorongoro volcanos, drains directly into the northeast end of the lake. Flow from the Budahaya / Udahaya River, which drains into the Yaeda Swamp to the southeast of the lake, was once second, but has decreased due to water diversion in the Mbulu Highlands. Water flow from the Serengeti is minor; the largest stream is the Sayu.
