Phenacogrammus is a genus of African tetras in the family Alestidae, native to the Congo River basin across the Democratic Republic of Congo, the Republic of Congo, and Gabon. The atlas covers 7 species ranging from about 1 in up to 4 in, and the genus is built on a deep-bodied, laterally compressed frame with large, iridescent scales that shift through blue, violet, and gold depending on the angle of light. Males typically carry elongated, trailing rays in the dorsal and caudal fins, a trait that becomes especially pronounced with age and is one of the clearest ways to tell the sexes apart in this genus.
This is one of the most recognizable genera in the whole tetra section of the hobby, carried almost entirely by Phenacogrammus interruptus, the Congo tetra, whose flowing fins and shimmering colour have made it a community-aquarium staple for decades. Other named species in the atlas, such as the orange Congo tetra (P. aurantiacus) and Poll's Congo tetra (P. polli), are far less commonly traded but share the same schooling, open-water temperament and preference for soft, slightly acidic blackwater-type conditions typical of Congo basin streams. Most assessed species are Least Concern, and several remain Not Evaluated, which fits a genus whose non-flagship species have drawn comparatively little dedicated conservation study.