Catholic Diocese of Kitui is found in the ecclesiastical region of Kenya and it is within the Nairobi metropolitan. It covers the whole Kitui County which is comprised of the following districts: Kitui West, Kitui Central, Lower Yatta, Nzambani, Mutitu, Mwingi Central, Mwingi West, Mwingi East, Kyuso, Mutomo, Mumoni, Tseikuru, Katulani, Mwingi West, Matinyani, Kisasi and Ikutha. It is an arid and semi-arid area of approximately 30,496.4 sq. Kms in Eastern Kenya, with a population of around 1,012,709 people according to 2009 census statistics. The Diocese has over 240,000 baptized Catholics.
The first Missionaries to evangelize Kitui were Holy Ghost Fathers from Kabaa (Machakos) in early 1930s. Also, by the time the Holy Ghost Fathers were introducing Christianity in Kitui, the Consolata Missionaries from Meru were evangelizing in the northern region of Kitui (now Kimangau). The first Mission house was built in 1945 at Mutune. Kitui Apostolic Prefecture was curved from the Archdiocese of Nairobi in 1956 under care of St. Patricks Kiltegan Missionaries,