Kiambu District was an administrative district in the Central Province of Kenya. Its capital town was Kiambu. The district was adjacent to the northern border of Nairobi and has a population of 744,010.^[1]

Created during the colonial era, it underwent changes, absorbing part Thika District, losing some of its regions to Nairobi such as Dagoretti while gaining some including Ruiru.^[2][3][4] By the 1970s, Thika District had been completely absorbed by its neighbouring districts, and Kiambu District was identical to the present-day Kiambu County. After 1992, Thika District was re-established from southwestern regions of Kiambu. In 2009, Thika District was declared unlawfully created and was reabsorbed to Kiambu yet again. In 2013, Kiambu County was effected on the same boundaries as the district absorbing it in the process.

The district was predominantly rural, but its urban population is increasing as Nairobi is growing rapidly. Kikuyu are the dominant tribe in the district.

In 2007, Kiambu District was subdivided in two: Kiambu East and Kiambu West. Kiambu West district took Limuru, Lari and Kikuyu divisions,^[5] with Limuru as its district capital.