All Parabuthus species from Eritrea, Ethiopia, and Somaliland were newly collected and are revised for the first time. The complex of Parabuthus liosoma is split into three sibling species with separate areas of distribution: P. abyssinicus Pocock, 1901 (Eritrea, Djibouti, central and north-eastern parts of Ethiopia), P. liosoma (Ehrenberg, 1828) (Yemen and Saudi Arabia), and P. maximus Werner, 1913 (Tanzania and Kenya). P. hamar sp. n. and P. kajibu sp. n., discovered during scorpiological expeditions in 2011–2016, are described. Information is provided about all Parabuthus species from the Horn of Africa, their taxonomy, distribution, and ecology, fully complemented with color photos of live and preserved specimens, as well as their habitat. The hemispermatophores of P. abyssinicus and P. kajibu sp. n. are illustrated and described. In addition to the analyses of external morphology and hemispermatophores, we also describe the karyotypes of P. abyssinicus (2n=16), P. kajibu sp. n. (2n=18), and P. pallidus (2n=20). The monotypic genus Riftobuthus Lourenço, Duhem et Cloudsley-Thompson, 2010 is synonymized with Parabuthus, based in part on pectinal tooth count analysis. Phylogenetic scaling and ontogenetic invariance of pectinal tooth count are shown for buthid scorpions.