During a taxonomic treatment of Stryphnodendron (Leguminosae, Caesalpinioideae, mimosoid clade) for the Brazilian Flora 2020 Project, one new presumably critically endangered species from the Atlantic Forest domain was found, and is so far only known to western Espírito Santo state. Stryphnodendron flavotomentosum is described and illustrated, and information on its distribution, habitat, phenology, and preliminary conservation status is provided. Additionally, an identification key for the species of Stryphnodendron from the Brazilian rainforests is presented.