Mwanza City, also known as Rock City to the residents, is a port city and capital of Mwanza Region on the southern shore of Lake Victoria in north-western Tanzania. With an urban population of 1,311,000 in 2023, it is Tanzania's second largest city, after Dar es Salaam. It is also the second largest city in the Lake Victoria basin after Kampala, Uganda and ahead of Kisumu, Kenya at least in population size. Within the East African community, Mwanza city is the fifth largest city after Dar, Nairobi, Mombasa, and Kampala. It is slightly ahead of Kigali, Kisumu, and Bujumbura in the population of city proper limits. Mwanza city is also the capital city of Mwanza Region, and is administratively divided into two municipal districts within that Region - Ilemela and Nyamagana.

Mwanza Region is one of Tanzania's 31 administrative regions. The region covers a land area of 25,233 km2 (9,743 sq mi). The region is comparable in size to the combined land area of the nation state of North Macedonia. Mwanza Region is bordered to the north through Lake Victoria by the Kagera Region and Mara Region, to the east by Simiyu Region, to the south by the Shinyanga Region and to the west by Geita Region. The regional capital is the city of Mwanza. According to the 2022 national census, the region had a population of 3,699,872 and national census of 2012 had 2,772,509. Mwanza Region is the second region with high population in Tanzania after Dar es Salaam Region.