In this paper, we show that Minkowski Functionals (MFs) of weak gravitational lensing (WL) convergence maps contain significant non-Gaussian, cosmology-dependent information. To do this, we run a large suite of cosmological ray-tracing N-body simulations to create mock weak WL convergence maps, and study the cosmological information content of MFs derived from these maps. Our suite consists of 80 independent 512 3 N-body runs, covering seven different cosmologies, varying three cosmological parameters Ωm, w, and σ8 one at a time, around a fiducial ΛCDM model. In each cosmology, we use ray-tracing to create a thousand pseudo-independent 12 deg 2 convergence maps, and use these in a Monte Carlo procedure to estimate the joint confidence contours on the above three parameters. We include redshift tomography at three different source redshifts zs = 1, 1.5, 2, explore five different smoothing scales θG = 1, 2, 3, 5, 10 arcmin, and explicitly compare and combine the MFs with the WL power spectrum. We find that the MFs capture a substantial amount of information from non-Gaussian features of convergence maps, i.e. beyond the power spectrum. The MFs are particularly well suited to break degeneracies and to constrain the dark energy equation of state parameter w (by a factor of ≈ three better than from the power spectrum alone). The non-Gaussian information derives partly from the one-point function of the convergence (through V0, the "area" MF), and partly through non-linear spatial information (through combining different smoothing scales for V0, and through V1 and V2, the boundary length and genus MFs, respectively). In contrast to the power spectrum, the best constraints from the MFs are obtained only when multiple smoothing scales are combined.