The United Nations Office (UNO) at Nairobi in Nairobi, the capital of Kenya, is one of four major United Nations office sites where numerous different UN agencies have a joint presence. Established in 1996, it is the UN's official headquarters in Africa.

Nairobi is the capital and largest city of Kenya. The name is derived from the Maasai phrase Enkare Nairobi, which translates to 'place of cool waters', a reference to the Nairobi River which flows through the city. The city proper had a population of 4,397,073 in the 2019 census. The Greater Nairobi Metropolitan Area has a population of about 7,000,000 people. The city is commonly referred to as The Green City in the Sun.