| Summary: | <i>Ceratozamia dominguezii</i> (Zamiaceae), a new species endemic to the lowland karstic tropical rainforests of southeastern Veracruz, Mexico, is described. The new species is part of the <i>C. robusta</i> species complex, a group of closely related species that share unique characteristics in the genus, such as robust trunks, large strobili, and long leaves. Compared with the other species in the complex (i.e., <i>C. robusta</i>, <i>C. leptoceras</i>, <i>C. aurantiaca</i> and <i>C. subroseophylla</i>), <i>C. dominguezii</i> has the longest rachides, and is characterized by having papyraceous leaflets, a unique caramel color in emerging leaves, and a dark-violet color in the central portion of distal faces of male and female sporophylls. <i>Ceratozamia dominguezii</i> occurs within the Uxpanapa floristic refuge, which is hypothesized to have sheltered a numerous group of tropical elements during the Neogene glaciations. The recognition of <i>C. dominguezii</i> contributes to clarifying the present diversity of cycads in the genus <i>Ceratozamia</i>, and adds discussion on the role of floristic refugia in the divergence of Neotropical plants in Mexico.
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