Kisumu, officially known as Kisumu City (and formerly Port Florence), is the Kenyan inland port city on Lake Victoria and the capital city of Kisumu County, Kenya. At an elevation of 1,131 m (3,711 ft), the city has an estimated population of 500,000, while the metropolitan region comprising the city and its suburbs and satellite towns of Maseno, Kondele and Ahero was estimated at over 1.5 million as of 2017. It is the third largest city in Kenya after the capital, Nairobi, and the coastal city of Mombasa. Kisumu is the principal city of western Kenya, the immediate former capital of Nyanza Province, the headquarters of Kisumu County and the proposed headquarters of the Lake Region Economic Block, which is a conglomeration of 15 counties in Western Kenya. It is the largest city in western Kenya and the second most important city after Kampala in the greater Lake Victoria basin. Kisumu International Airport serves the city with regular flights to Nairobi and other neighboring cities such as Kampala, Mwanza, and Kigali.
Kisumu port was founded in 1901 as the main inland terminal of the Uganda Railway named "Port Florence". Although trade stagnated in the 1980s and 1990s, it is again growing around oil exports.
Kisumu literally means a place of barter trade "sumo". The city has "Friendship" status with Cheltenham, United Kingdom and "sister city" status with Roanoke, Virginia and Boulder, Colorado, United States.