In finite group theory, a branch of mathematics, the Thompson subgroup of a finitep-groupP refers to one of several characteristic subgroups of P. John G. Thompson (1964) originally defined to be the subgroup generated by the abeliansubgroups of P of maximal rank. More often the Thompson subgroup is defined to be the subgroup generated by the abelian subgroups of P of maximal order or the subgroup generated by the elementary abelian subgroups of P of maximal rank. In general these three subgroups can be different, though they are all called the Thompson subgroup and denoted by .