A new species of isosporoid coccidia (Apicomplexa: Eimeriidae) is described from captive Himalayan Black Bulbul Hypsipetes leucocephalus (Passeriformes: Pycnonotidae). Sporulated oocysts of Isospora annthomassonae n. sp. are subspherical to slightly ellipsoidal 32.0 ± 1.5 × 29.4 ± 1.3 (30–35 × 27–31) μm. Micropyle, oocyst residuum and polar granule are absent. Sporocysts are broadly ellipsoidal, 24.6 ± 1.4 × 12.9 ± 0.7 (22–28 × 12–14) μm, with Stieda and substiedal bodies. Sporocyst residuum is broadly ellipsoidal, 11.3 ± 0.8 × 9.5 ± 0.7 (9–13 × 8–11) μm, composed of hundreds of small granules. Sporozoites are elongate and slightly curved, each with two refractile bodies.
