A theory that attempts to unify gravitation with the other fundamental interactions. The first, and only, completely successful unified theory was constructed by James Clerk Maxwell, in which the up-to-then unrelated electric and magnetic phenomena were unified in his electrodynamics. Early in the twentieth century, the problem of unifying electrodynamics and gravitation into a single theory was pursued. Later, with the discovery of weak and strong nuclear forces, it became clear that the unification problem was more complex than had been anticipated, and, moreover, that a more attainable goal on the way to full unification was to first unify electromagnetic, weak, and possibly strong forces. If successful, the next step would be unification with gravity into a superunified theory.

Supergravity models are special superunified theories. To put the aims and the achievements of these models in a proper perspective, it will be helpful to briefly recount the earlier stages of unification.