A new genus of cynipid oak gallwasp, Zapatella Pujade-Villar & Melika, gen. n. (Hymenoptera: Cynipidae: Cynipini), with two new species, Zapatella grahami Pujade-Villar & Melika, sp. n. and Z. nievesaldreyi Melika & Pujade-Villar, sp. n., is described from the Neotropics. Zapatella grahami, known only from the sexual generation, induces galls in acorns of Quercus costaricensis and is currently known only from Costa Rica. Zapatella nievesaldreyi, known only from the asexual generation, induces inconspicuous galls in twigs of Q. humboldtii, and is known only from Colombia. Diagnostic characters for both new species are given in detail. Five Nearctic species are transferred from Callirhytis to Zapatella: Z. cryptica (Weld), comb. n., Z. herberti (Weld), comb. n., Z. oblata (Weld), comb. n., Z. quercusmedullae (Ashmead), comb. n., Z. quercusphellos (Osten Sacken), comb. n. (= Z. quercussimilis (Bassett), syn. n.). A key based on adults for the species belonging to Zapatella is also given. Generic limits and morphological characteristics of Zapatella and closely related genera are discussed.