M-theory origin of mirror symmetry in three-dimensional gauge theories

We present M-theory compactifications on K3 × K3 with membranes near the An or Dn singularities of the K3 spaces. By realizing each of these compactifications in two different ways as type I′ models with 2- and 6-branes, we explain the three-dimensional duality between gauge theories recently found by Intriligator and Seiberg. We also find new pairs of dual gauge theories, which we briefly describe.