A new species of coccidia (Protozoa: Apicomplexa: Eimeriidae) found parasitizing the white-eyed parakeet Psittacara leucophthalmus (Müller, 1776) in Brazil is described. Eimeria psittacarae n. sp. has oocysts that are ellipsoidal, 34.8 × 24.3 μm, with smooth, bilayered wall, ~1.7 μm thick. Micropyle present. Oocyst residuum absent, but one or two polar granules are present. Sporocysts are elongate ellipsoidal, 19.2 × 9.7 μm. Stieda body knob-like and sub-Stieda body rounded. Sporocyst residuum is composed of granules that appear to be membrane-bounded. Sporozoites are vermiform with one refractile body and a nucleus. This is the sixth description of an eimeriid coccidium parasitizing a New World psittacine.
Keywords: Protist, taxonomy, morphology, coccidia, Eimeria, oocysts, Psittaciformes, Psittacidae, Serra dos Órgãos National Park, Rio de Janeiro, Brazil.