Sub-counties, formerly known as Districts, are the decentralised units through which government of Kenya provides functions and services. At national level, sub-counties take a more administrative function like security, statistical purposes, provision of government services, etc. Even though the sub-counties are divisions of counties, powers to create new national sub-counties lies with the national government. As of 2023, there are 314 sub-counties, compared to 290 constituencies. A deputy county commissioner is appointed by the state to lead each sub-county. The sub-counties are further divided into divisions, locations and sub-locations.
Districts were introduced in Kenya by the colonial government to ease control and management of the colony. The number of districts in Kenya through the colonial period varied. Headed by District Commissioners (DC), districts were the second level of administration after the provinces. In 1962, as the colony was transitioning to self-rule, the colonial government redrew the districts and capped them at forty, in addition to the Nairobi Area. A bicameral parliament meant that the districts were to send one senator to the Senate. In 1966, the Senate was abolished by an amendment to the constitution, making the districts purely administrative. By 1992, one district had been eliminated, six more had been created by splitting some of the existing districts. By the start of the 21st century more districts had been created, and by 2005, seventy two districts were in existence, and by 2010, Kenya had 265 districts. In 2009, the High Court declared all districts created after 1992 unlawful, though they remained functional.