Alcantarea galactea (Bromeliaceae, Tillandsioideae), a new species of giant bromeliad from the inselbergs of the state of Espírito Santo, southeastern Brazil, is described and illustrated. A distribution map and a table with the main characteristics used to distinguish the new species from its morphologically similar relatives are presented. Alcantarea galactea is among the largest species of this genus, differing from related taxa by its larger habit, leaves densely covered by a thick layer of white epicuticular wax, and spreading stamens. So far, the species is only known from Alfredo Chaves municipality. The areas nearby the type locality have been strongly disturbed by grazing, logging, expansion of coffee plantations, and granite mining. This species may be considered as endangered. Nevertheless, both populations so far known are large enough to be seen from great distances, including aerial photos, and this is one of the motivations for the epithet chosen here, together with the white pulverulent leaves.