Kisumu is the third-largest city in Kenya after the capital, Nairobi, and Mombasa. It is the second-largest city after Kampala in the Lake Victoria Basin. The city has a population of slightly over 600,000. The metro region, including Maseno and Ahero, has a population of 1,155,574 people according to the 2019 Kenya Population and Housing Census which was conducted by the Kenya National Bureau of Statistics.

Lake Victoria is one of the African Great Lakes. With a surface area of approximately 59,947 km2 (23,146 sq mi), Lake Victoria is Africa's largest lake by area, the world's largest tropical lake, and the world's second-largest fresh water lake by surface area after Lake Superior in North America. In terms of volume, Lake Victoria is the world's ninth-largest continental lake, containing about 2,424 km3 (1.965×109 acre⋅ft) of water. Lake Victoria occupies a shallow depression in Africa. The lake has an average depth of 40 m (130 ft) and a maximum depth of 80–81 m (262–266 ft). Its catchment area covers 169,858 km2 (65,583 sq mi). The lake has a shoreline of 7,142 km (4,438 mi) when digitized at the 1:25,000 level, with islands constituting 3.7% of this length.