Eimeria trichechi n.sp. is described and figured from the manatee, Trichechus inunguis, from Amazonas State, north Brazil. Undifferentiated oocysts are passed in the faeces and complete their sporulation in ∼36h at 24 to 26°C. Oocysts are spherical, with a mean size of 13.40 × 13.30 μm. The wall is uni-layered, smooth, colourless and ∼0.5 μm thick; there is no micropyle, oocyst residuum or polar body. Sporocysts are ellipsoidal, with a mean size of 8.65 × 4.62 μm. The sporozoites are longer than the sporocyst and recurved at their ends: there is a sporocyst residuum of fine granules, but no visible Steida body. ac]19821113