abstract: In this talk we will discuss joint work in collaboration with Christoph Böhm in which we obtain structure results for non-compact Einstein manifolds admitting a cocompact isometric action of a connected Lie group. As an application, we prove the Alekseevskii conjecture (1975): any connected homogeneous Einstein space of negative scalar curvature is diffeomorphic to a Euclidean space. If time permits, I will also present a more recent splitting result in the case of a semisimple group action.