A new species of the genus Heterometrus is described on the basis of a specimen recently collected in Thailand. Heterometrus minotaurus sp. nov. is morphologically closest to H. longimanus. The newly described species is well distinguished by its smaller overall size (83 mm) and shorter and less narrow metasoma with specific dorsolateral carinae on the fourth metasomal segment consisting of 9 or fewer granules. No females are known and so knowledge of sexual dimorphism in this species is currently lacking. In addition to the morphological characterization of H. minotaurus sp. nov., we present here also a description of the male holotype's karyotype. The diploid set of H. minotaurus sp. nov. consists of 54 chromosomes with a predominance of metacentrics, which gradually decrease in size. The presence of two types of multivalent association observed in postpachytene and metaphase I is commented on. Current knowledge of karyotypes of Heterometrus species is briefly summarized and compared with our cytogenetic results. In conclusion, we discuss the possible usefulness of karyotype as another interspecific feature applicable in the taxonomy of this scorpion group.