EN
A new isosporoid coccidian (Apicomplexa, Eimeriidae) species from the grey-hooded flycatcher, Mionectes rufiventris, from Brazil, is reported in the current study. Isospora mionectesi sp. nov. oocysts are ellipsoidal, 28.3 × 21.2 µm, with smooth, bilayered wall, ∼1.3 µm. Micropyle and oocyst residuum are absent, but one or two polar granules are present. Sporocysts are elongate ellipsoidal, 19.7 × 11.7 µm. Stieda body rounded and substieda body prominent. Sporocyst residuum is subspherical and compact. Sporozoites are vermiform with one refractile body and a nucleus.