Black Kei River, (Afrikaans:Swart-Kei Rivier), originates southwest of Queenstown, and eventually joins the White Kei River, to become the Great Kei River. Several villages are situated on its banks, including McBride Village, Qabi, Ntabelanga, Thornhill, Loudon, Mitford, Basoto, Baccle's Farm and Tentergate.
The Thrift Dam is its only significant reservoir.
Its upper reaches form the western boundary of the Tsolwana Nature Reserve, and during the mid 1800's, the Black Kei and its Klipplaat tributary formed the northern boundary of British Kaffraria. The Xesana, Klaas Smits and Klipplaat rivers are its main tributaries.