  We investigate Levi subgroups of a connected reductive algebraic group G,
over a ground field K. We parametrize their conjugacy classes in terms of sets
of simple roots and we prove that two Levi K-subgroups of G are rationally
conjugate if and only if they are geometrically conjugate.
  These results are generalized to arbitrary connected linear algebraic
K-groups. In that setting the appropriate analogue of a Levi subgroup is
derived from the notion of a pseudo-parabolic subgroup.
