Swahili Language (or Kiswahili), African language, spoken in Eastern Africa and in parts of Central Africa in countries including Tanzania, Kenya, Rwanda, Burundi, the Comoros Islands, southern Somalia, and northern Mozambique. Swahili is also spoken among East African diaspora communities in Oman, the Gulf countries, in Europe, and North America. There are in Eastern Africa up to 50 million speakers of the language, the majority of whom are in Kenya and Tanzania, where Swahili is a national language. It is the lingua franca of the region.

Swahili belongs to the Bantu family of languages (see Niger-Congo Languages), which are spoken in the southern third of Africa, from Cameroon and Kenya to South Africa. The Swahili spoken in East Africa is different to Congo Swahili, spoken in the Democratic Republic of the Congo, which is a close relation; there are in fact six related languages in a subset (called Swahili) of the Bantu family. They share an extensive pool of common lexicon as well as an elaborate noun class system. Each noun in Swahili belongs to a particular class, denoted by a specific prefix that agrees with similar affixes in adjectives, demonstratives, and relative clauses, for example, m + tu (“person”) m + zuri (“good”), “a good person”.

Swahili is divided into a number of dialects spoken along the East African coast and the islands, stretching from the Lamu archipelago in the north to Comoros in the south. Kiamu (Amu), Kipate (Pate), Kisiu (Siu or Siyu), and Kimvita (Mvita) constitute major northern dialects; southern dialects include Kiunguja (Unguja), spoken in Zanzibar city, and Kipemba (Pemba), itself divided further into smaller dialects. Contact with Arab traders over centuries on the East African coast provided Swahili with its first script, the Swahili-Arabic script, in which literary works, dating from at least the 17th century, were written. A significant number of loanwords from Arabic entered Swahili during this period, especially in the fields of commerce, religion, and social relations. Later, German and then British colonial administrators encouraged the use of Swahili in schools, the civil service, the police, and other areas of government, thus aiding its spread in the region. In 1930, Kiunguja (of Zanzibar) was adopted as standard Swahili and the Latin script as its orthography. English has today replaced Arabic as the main provider of loanwords.