Using a combination of morphological, life-cycle and molecular data, we describe a new apicomplexan parasite Eimeria telekii n.sp. from a striped grass mouse Lemniscomys striatus captured in Kenya. Oocysts are oval to spherical or ellipsoidal, 20·4×15·7 (15·5–25·0×12·0–20·0)μm with a colourless, smooth and bilayered wall. Sporocysts are ellipsoidal, 11·2×7·8 (10·0–12·0×7·0–9·0)μm with a small Stieda body and granular sporocyst residuum and contain 2 elongated, banana-shaped sporozoites with a single refractile body. Life-cycle, pathogenicity and host specificity of this parasite were studied in laboratory-bred Lemniscomys barbarus and BALB/c mice. Two asexual stages and the sexual phase took place within the enterocytes of the caecum and colon of L. barbarus but not in inoculated BALB/c mice. An infectious dose of 5000 oocysts caused severe clinical illness and mortality in 2/2 (100%) L. barbarus. Phylogenetic analysis of the small subunit rRNA gene of E. telekii and members of the genera Eimeria, Cyclospora and Isospora placed E. telekii within the eimerian rodent clade.The nucleotide sequence was deposited in the GenBankTM under the accession number AF246717.