Macrozamia, genus of about 40 species of palmlike cycads in the family Zamiaceae, native to Australia and grown elsewhere as ornamental and conservatory specimens. The genus includes tuberous fernlike plants and palmlike columnar trees. The pith is a source of starch, but the seeds are poisonous to livestock. The large female and male cones are borne on separate individuals. Members of the genus Lepidozamia were formerly placed in the genus Macrozamia.