From the Wikipedia page 
Rukwa Region is one of Tanzania's 31 administrative regions. The regional capital is the municipality of Sumbawanga. According to the 2012 national census, the region had a population of 1,004,539.
The region is bordered to the north by the Katavi Region, to the east by the Mbeya Region, to the south by Zambia, and to the west by Lake Tanganyika, which forms a border between Tanzania and the Democratic Republic of the Congo.