Kajiado County is a county in Kenya. It is located in the south of the country and is border with Tanzania. Its capital is Kajiado, but the most important locality is Ngong. The total population of the county is of 687 312 inhabitants according to the census of 2009. Good part of its population situates within the metropolitan area of Nairobi. In this county are the Amboseli National Park and the Nyiri Desert.