A turbulent behaviour of wave patterns is described, which is related to the presence of dislocations. By means of numerical simulations of 2D complex Ginzburg-Landau equations, it is shown that phase instability leads in spatially extended systems to spontaneous nucleation of topological defects. The appearance of these localized amplitude perturbations is interpreted as the consequence of the revolt of the slaved amplitude modes. Once created, those defects move through the system and break the order induced by the wave pattern. The resulting turbulent state has been termed "topological turbulence".