Kiambu County is a county in the former Central Province of Kenya. Its capital is Kiambu and its largest town is Thika.
Kiambu County borders Nairobi and Kajiado Counties to the South, Machakos to the East, Murang‘a to the North and North East, Nyandarua to the North West, and Nakuru to the West and has a population of 2,417,735.
The county is 40% rural and 60% urban owing to Nairobi's consistent growth Northwards. Kikuyu are the dominant tribe in the county.
In 2007, Kiambu District was subdivided in two: Kiambu East and Kiambu West. Kiambu West district took Limuru, Lari and Kikuyu divisions, with Limuru as its district capital.