The monotypic genus Algrizea is described from the Chapada Diamantina highlands, in Bahia, Brazil, and a new combination, Algrizea macrochlamys, is proposed. This species was well-known from flowering material but fruits and seeds, essential for accurate generic placement, were unknown until 2000. Treated successively as Myrcia, Myrtus, and more recently as Psidium, it combines characters usually considered primitive in the Myrtaceae with an unusual embryo unlike any hitherto described in the Myrtaceae. Morphological and preliminary molecular data suggest that it is best accommodated in the Myrciinae sensu stricto. Algrizea is distinguished by the combination of 3-flowered dichasia, persistent bracteoles, 5 well-developed calyx lobes, bilocular ovaries with 3–6(-8) ovules per locule, seeds 2–3 with membranous, shiny testa, and an embryo in which the hypocotyl assumes an internal position to the unequal, sheathing cotyledons.