Koinadugu District is a district in the Northern Province of Sierra Leone. It is the largest District in Sierra Leone in geographical area, and one of the least most densely populated. Its capital and largest city is Kabala, which is also one of the main cities in Northern Sierra Leone. The District of Koinadugu has a population of 404,097, based on the 2015 Sierra Leone national census; and has a total area of 12,121 km2 (4,680 sq mi). Koinadugu District is subdivided into eleven chiefdoms.
The District of Koinadugu borders Bombali on the west, Tonkolili District to the south-west, Kono District to the south, Falaba District to the east, and the Republic of Guinea to north east. Diamond mining is a major economic activity in the district, as well as agricultural production of rice, mango, cacao, and coconut.
The population of Koinadugu district is almost entirely made up of five main ethnic groups: the Kuranko, Mandingo, Fula, Limba, and Yalunka. These five ethnic groups are politically and culturally influential in Koinadugu District. Koinadugu District is overwhelmingly Muslim majority at over 90% and Islam dominates the religious and cultural practices in the district. There is also a small but significant minority Christian population in the district, and is mainly among the Limba people in the district.