Nairobi ( /naɪˈroʊbi/) is the capital and largest city of Kenya. The city and its surrounding area also forms the Nairobi County. The name "Nairobi" comes from the Maasai phrase Enkare Nairobi, which translates to "cold water," the Maasai name of the Nairobi river, which in turn lent its name to the city. However, it is popularly known as the "Green City in the Sun" and is surrounded by several expanding villa suburbs. Residents of Nairobi are known as Nairobians.

Founded by the British in 1899 as a simple rail depot on the railway linking Mombasa to Uganda, the town quickly grew to become the capital of British East Africa in 1907 and eventually the capital of a free Kenyan republic in 1963. During Kenya's colonial period, the city became a centre for the colony's coffee, tea and sisal industry. Nairobi is also the capital of the Nairobi Province and of the Nairobi District. The city lies on the Nairobi River, in the south of the nation, and has an elevation of 1795 m above sea-level.