Northwestern African Buthacus species are revised. Buthacus stockmanni sp. n. from Morocco and Western Sahara is described and fully complemented with color photos of live and preserved specimens, as well as their habitat. The hemispermatophore of B. stockmanni sp. n. is illustrated and described. In addition to morphology and hemi-spermatophores, we also describe the karyotypes of B. stockmanni sp. n. (2n=20). B. stockmanni sp. n. is compared with B. occidentalis Vachon, 1953 and B. ziegleri Lourenço, 2000. Both these species are differentiated from B. stockmanni sp. n. geographically and morphologically. The male of B. stockmanni sp. n. has fingers of pedipalp chela strongly twisted proximally and males of the other two species have fingers straight or almost straight. Buthacus huberi Lourenço, 2001 is synonymized with Buthacus occidentalis Vachon, 1953; Buthacus mahraouii Lourenço, 2004 and Buthacus leptochelys algerianus Lourenço, 2006 are synonymized with Buthacus ziegleri Lourenço, 2000.