Anton S. Desyatnikov Nonlinear Physics Centre, Research School of Physics and Engineering, The Australian National University Nonlinear dynamics of optical vortices Optical vortices are threads of darkness in laser beams. Despite vanishing intensity at the vortex cores their dynamics is strongly affected by nonlinearity. I will discuss two systems with unusual vortex transformations. First is the bulk Kerr-type medium where the combination of nonlinear self-phase modulation of an elliptic laser beam and its spatial twist introduced by optical orbital angular momentum leads to spontaneous nucleation and knotting of optical vortex lines. Second system is a ring of coupled nonlinear waveguides (oscillators) which supports surprisingly rich variety of discrete vortex modes and solitons. An overview of our recent results will cover systems featuring Fano resonances, PT-symmetric defects, and coupled optical waveguides with positive and negative refractive indices.