We present a semiclassical prediction of regular-to-chaotic tunneling in systems with a mixed phase space, including the effect of a nonlinear resonance chain. We identify complex paths for direct and resonance-assisted tunneling in the phase space of an integrable approximation with one nonlinear resonance chain. We evaluate the resonance-assisted contribution analytically and give a prediction based on just a few properties of the classical phase space. For the standard map excellent agreement with numerically determined tunneling rates is observed. The results should similarly apply to ionization rates and quality factors.Tunneling through energetic barriers is a textbook paradigm of quantum mechanics. While classically motion is confined to either side of the barrier, wave functions exhibit contributions on both sides. In contrast, nature often exhibits confinement on dynamically disjoint regions of regular and chaotic motion in a mixed phase space, see Fig. 1(a). Here, a classical particle follows a trajectory of regular motion while the correponding wave function admits an exponentially small contribution on the chaotic region. This phenomenon is called dynamical tunneling [1,2].Until today dynamical tunneling has emerged in many fields of physics. It determines the vibrational spectrum of molecules [1], ionization rates of atoms in laser fields [3,4], and chaos-assisted tunneling oscillations [5,6] in cold atom systems [7,8]. In optics dynamical tunneling is experimentally explored in microwave resonators [9][10][11][12] as well as microlasers [13][14][15][16][17][18][19][20], where it determines the quality factor of lasing modes. Here, a recent experimental breakthrough [12,17] is the measured enhancement of dynamical tunneling due to nonlinear resonance chains [21,22].To reveal the universal features of dynamical tunneling it is extensively studied theoretically [10,13, mainly in model systems. A central object is the tunneling rate γ m , which describes the transition from a state on the mth quantizing torus of the regular region into the chaotic sea. Qualitatively γ m can be understood from the theory of resonance-assisted tunneling [21,22,27,44], see dashed line in Fig. 1(b): On average γ m decreases exponentially for decreasing wavelength or decreasing effective Planck constant, i.e. Plancks constant scaled to some typical action of the system. In addition a drastic enhancement of γ m is observed for some values of h. This is due to resonant coupling of regular states, induced by a nonlinear resonance chain [45] within the regular region, see Fig. 1 In this paper we establish an intuitive, semiclassical,