We show that nonlinear resonances in a classically mixed phase space allow to define generic, strongly entangled multi-partite quantum states. The robustness of their multipartite entanglement increases with the particle number, i.e. in the semiclassical limit, for those classes of diffusive noise which assist the quantum-classical transition.PACS numbers: 03.65. Yz, 03.67.Lx,03.67.Mn,03.67.Pp, 05.45.Mt The ultimate success of the quantum information and computation program will depend on our theoretical understanding and experimental control of quantum entanglement. In order to compete with the available classical supercomputing resources, a future quantum computer will have to be composed of a large, i.e., at least mesoscopic number of qubits, and their coherence will need to be preserved over a significant period of time. Contemplating the fact that entanglement is a manifestation of multi-particle coherence, and that the density of states explodes exponentially with the particle number, it is easy to appreciate the dimension of the challenge ahead.So far, little is known about entanglement in open quantum systems -where "open" refers to the unavoidable coupling to uncontrolled degrees of freedom in the "environment", which eventually induces decoherence in the system dynamics. Only recently [1,2,3,4,5,6,7] have there been first theoretical and experimental attempts to characterize entanglement dynamics under decoherence, but a sufficiently general picture still has to emerge. In particular, most studies did so far focus on specific classes of highly entangled W, GHZ, or cluster states, and on their specific robustness against certain sources of decoherence [8,9]. As the number of particles increases, the faithful experimental generation and probing of these states tends to become more and more difficult, with rapidly increasing experimental overhead. Furthermore, whether and in which sense their entanglement properties can be considered as "generic" is a largely open issue, given the complicated topology of state space.In our present contribution, we will adopt a different perspective, which imports some generic features of quantum dynamics with underlying mixed, regular-chaotic phase space structure, i.e., from quantum chaos [10]. In contrast to earlier studies of the impact of mixed phase space dynamics [11,12,13] and nonlinear light-matter interaction [14,15] on bipartite entanglement, we are here interested in the multipartite limit of large particle numbers. This is of crucial importance in the context of entanglement scaling alluded to above, and will be identified with the semiclassical limit of progressively finer (quantum) resolution of classical phase space structures, by a suitable definition of many-particle basis states in terms of classical phase space coordinates. We will see that nonlinear resonances, which are ubiquitous in classical Hamiltonian systems [16], naturally define strongly -though not maximally -entangled multipartite quantum states. This non-optimality is compensated by the n...