Clusia magnoliiflora M. H. G. Gust. is described as new for the Clusiaceae. It grows in dry scrub in the river valleys of the Marañón and its tributaries in northern Peru, a kind of habitat that harbors very few Clusia species. The species is distinct on account of its extremely thick, obovate leaves; the large, white flowers with as many as seven or eight spatulate petals; the large, white, triangular stigmata in the flower; and the spherical fruit with the stigmata positioned well below the apex. Clusia magnoliiflora is abundant in the habitat where it was collected.