  We present a comprehensive classification of supersymmetric vacua of M-theory
compactification on seven-dimensional manifolds with general four-form fluxes.
We analyze the cases where the resulting four-dimensional vacua have N =
1,2,3,4 supersymmetry and the internal space allows for SU(2), SU(3) or G_2
structures. In particular, we find for N = 2 supersymmetry, that the external
space-time is Minkowski and the base manifold of the internal space is
conformally K\"ahler for SU(2) structures, while for SU(3) structures the
internal space has to be Einstein-Sasaki and no internal fluxes are allowed.
Moreover, we provide a new vacuum with N = 1 supersymmetry and SU(3) structure,
where all fluxes are non-zero and the first order differential equations are
solved.
