A new species in the genus Zamia (Zamiaceae), Z. gentryi, from northwestern Ecuador is described. This arborescent species appears to be most closely allied to Z. roezlii Linden, with which it grows sympatrically along the margins of the populations. Zamia gentryi is occasionally found growing as an epiphyte. Character states that distinguish the two species are presented. The genus Zamia is restricted to the tropics and subtropics of the Western Hemisphere, where about 55 species are recognized as valid. Another five (or more) species are recognized but have not been for- mally described. Four species have been reported from Ecuador with Z. amplifolia Hort ex Masters, Z. lindenii Regel ex Andre, and Z. roezlii Linden known from the western side, and Z. ulei Dammer vel aff. from the Amazon drainage. Zamia poeppi- giana Martius & Eichler has been reported from southeastern Ecuador but no specimens have been seen. Some cycad specialists consider Z. lindenii to be synonymous with Z. poeppigiana. I do not consider them to be the same.