The first fossil ribbonfish, Trachipterus mauritanicus sp. nov., based on a single specimen, is described from Sidi-Brahim, an Upper Miocene (Messinian) locality situated in the central sector of the Chelif Basin, northwestern Algeria. Trachipterus mauritanicus sp. nov. is characterized by a flattened neurocranium and an advanced insertion of the dorsal fin. Based on skeletal morphology, T. mauritanicus sp. nov. appears to be related to T. arawatae and T. trachypterus. Trachipterus mauritanicus sp. nov. represents the eighth taxon described up to now from Sidi-Brahim. The occurrence of the first fossil member of the family Trachipteridae from the Upper Miocene sediments of northwestern Algeria emphasizes the crucial importance of the Messinian ichthyofaunas from Algeria to our knowledge of the fossil record of the Teleostei.