The threadfin cichlid (Petrochromis trewavasae) is a species of cichlid endemic to Lake Tanganyika found in areas with rocky substrates on which it can graze on algae.

This species can reach a length of 18 cm (7.1 in).

It can be found in the aquarium trade.

[2] The specific name of this cichlid honours the British ichthyologist Ethelwynn Trewavas (1900-1993).

This Cichlidae-related article is a stub.