Quassia (/ˈkwɒʃə/ or /ˈkwɒʃiə/) is a plant genus in the family Simaroubaceae. Its size is disputed; some botanists treat it as consisting of only one species, Quassia amara from tropical South America, while others treat it in a wide circumscription as a pantropical genus containing up to 40 species of trees and shrubs. The genus was named after a former slave from Suriname, Graman Quassi in the eighteenth century. He discovered the medicinal properties of the bark of Quassia amara.