  Quantum mechanics is not the unique no-signaling theory which is endowed with
stronger-than-classical correlations, and there exists a broad class of
no-signaling theories allowing even stronger-than-quantum correlations. The
principle of information causality has been suggested to distinguish quantum
theory from these nonphysical theories, together with an elegant
information-theoretic proof of the quantum bound of two-particle correlations.
In this work, we extend this to genuine $N$-particle correlations that cannot
be reduced to mixtures of states in which a smaller number of particles are
entangled. We first express Svetlichny's inequality in terms of multipartite
no-signaling boxes, then prove that the strongest genuine multipartite
correlations lead to the maximal violation of information causality. The
maximal genuine multipartite correlations under the constraint of information
causality is found to be equal to the quantum mechanical bound. This result
consolidates information causality as a physical principle defining the
possible correlations allowed by nature, and provides intriguing insights into
the limits of genuine multipartite correlations in quantum theory.
