  We give an intrinsic definition of the special geometry which arises in
global N=2 supersymmetry in four dimensions. The base of an algebraic
integrable system exhibits this geometry, and with an integrality hypothesis
any special Kahler manifold is so related to an integrable system. The
cotangent bundle of a special Kahler manifold carries a hyperkahler metric. We
also define special geometry in supergravity in terms of the special geometry
in global supersymmetry.
