Nyanza Province (Mkoa wa Nyanza) was one of Kenya's eight administrative provinces before the formation of the 47 counties under the 2010 constitution. Six counties were organised in the area of the former province.
The region is located in the southwest part of Kenya around Lake Victoria, includes part of the eastern edge of Lake Victoria, and is inhabited predominantly by the Luo people. There are also Bantu-speaking tribes, such as the Gusii, the Kuria, and some Luhya, living in the province. The province derives its name from Nyanza, a Bantu word which means a large mass of water.
The provincial capital was Kisumu, the third-largest city in Kenya. The province had a population of 4,392,196 at the 1999 census within an area of 16.162 km², or 12.613 km² of land.
The climate is tropical humid.
The following counties make up the area of the former Nyanza province: