Kilwa District is one of six administrative districts of Lindi Region in Tanzania. The District covers an area of 15,000 km2 (5,800 sq mi). The district is comparable in size to the land area of the nation state of East Timor. Kilwa district is bordered to the north by Rufiji District in Pwani Region, to the east by the Indian Ocean, to the south by the Lindi District, Nachingwea District together with Ruangwa District, and to the west by the Liwale District. The district borders every other district in Lindi Region except Lindi Municipal District. The district seat (capital) is the town of Kilwa Masoko. The district is named after the medieval Swahili city state of Kilwa Kisiwani. According to the 2012 census, the district has a total population of 190,744. By 2022, the population had increased to 297,676.

Swahili, also known by its local name Kiswahili, is a Bantu language originally spoken by the Swahili people, who are found primarily in Tanzania, Kenya and Mozambique. The number of current Swahili speakers, be they native or second-language speakers, is estimated to be over 200 million, with Tanzania known to have most of the native speakers.