Kasulu District is one of the six districts of Kigoma Region, Tanzania. It is bordered to the north by Burundi, to the east by Kibondo District, to the south by Uvinza District, to the west by Kigoma District and to the northwest by Buhigwe District.
According to the 2002 Tanzania National Census, the population of the Kasulu District was 628,677.
Kasulu District is predominantly occupied by the "Waha" ethnic group. As per United Republic of Tanzania, 2002 Population and Housing Census, Kasulu population is 628,677 (299,506 males and 329,171 females) with a total of 85,572 households; an average family size is 7.3; it comprises 90 villages in 30 wards. As of 2011[update], Kasulu district was hosting two refugee camps namely Mtabila (for Burundians with 37,670 individuals) and Nyarugusu (for Congolese..Congo DRC with 62,440 individuals) The Mtabila camp has been ordered to be closed.
Main economic activity is subsistence farming and small and medium scale businesses especially in Kasulu town. There are a few "Wasukuma" ethnic group pastoralists who come into Kasulu with flocks of cattle in search of pastures. They normally purchase pieces of land for settlement for them and their cattle.
As of 2002[update], Kasulu District was administratively divided into thirty wards: However, administrative changes in 2012, removed some of the wards, for example Buhigwe.
Coordinates: 4°26′S 30°26′E / 4.44°S 30.44°E