Nyassa, a lake of East Africa, in the Zambesi basin, between lat. 9° and 14° S., and long. 34° and 36° E. Its elevation is about 1,550 feet, with a depth of over 140 fathoms in some places. The distance from north to south is 350 miles, and the average breadth about 40 miles. From the south extremity the river Shire flows to the Zambesi. The lake was discovered by Livingstone in 1859.