Sub-counties are the decentralized units through which county governments of Kenya will provide functions and services. Except for the parts which fall under urban areas, sub-counties will coincide with the constituencies created under article 89 of the Constitution of Kenya. Sub-counties will be headed by a sub-county administrator, appointed by a County Public Service Board.
Under the former Constitution of Kenya, the provinces of Kenya were subdivided into a number of districts (wilaya). In line with restructuring the national administration to fit with the devolved government system brought in by the 2010 Constitution, that came into full effect following elections in March 2013, the 8 provinces and their administrators and districts were replaced by County Commissioners at the county level, while former districts existing as of 2013 were re-organised as sub-counties, and had Deputy Commissioners appointed over them.
Following a High Court ruling in September 2009, there were 46 legal districts in Kenya, excluding Nairobi which constituted a 47th district.
Following the Kenyan general election, 2013, these districts and Nairobi now constitute the 47 counties which will be the basis for rolling out devolution as set out in the 2010 Constitution of Kenya (district headquarters are in parenthesis):