Astyanax microschemos is a species of characid fish from Brazil. It belongs to the A. scabripinnis species complex and differs from other species outside it by having a lower number of branched anal fin rays (about 14-18 vs 20-45) and its shallow body depth being about 26.9-29.7 vs more than 35% of its standard length (SL). Compared to species of its own complex, it can be distinguished by the combination of its shallow body depth (ranging from 26.9-29.7% of SL), and smaller interorbital width (26.9-30.4% of its head length). The species name comes from the Greek mikroschemos, meaning "low stature", which refers to the shallow body depth of the animal.