Indian subcontinent harbours both the human mtDNA macrohaplogroups M and N, of which M is the most prevalent. In this study, we discuss the overall distribution of the various haplogroups and sub-haplogroups of M among the different castes and tribes to understand their diverse pattern with respect to geographical location and linguistic affiliation of the populations. An overview of about 170 studied populations, belonging to four distinct linguistic families and inhabiting different geographic zones, revealed wide diversity of about 22 major haplogroups of M. The tribal populations belonging to the same linguistic family but inhabiting different geographical regions (Dravidian and Austro-Asiatic speakers) exhibited differences in their haplogroup diversity. The northern and southern region castes showed greater diversity than the castes of other regions.