Quassia (/ˈkwɒʃə/ or /ˈkwɒʃiə/) is a flora 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 Surinam, Graman Quassi in the eighteenth century. He discovered the medicinal properties of the bark of Quassia amara. Broader treatments of the genus include the following and other species: