  We prove that the Whitehead link complement and the (-2, 3, 8) pretzel link
complement are the minimal volume orientable hyperbolic 3-manifolds with two
cusps, with volume 3.66... = 4 x Catalan's constant. We use topological
arguments to establish the existence of an essential surface which provides a
lower bound on volume and strong constraints on the manifolds that realize that
lower bound.
