Abstract <p>A theoretical study is performed of a quasi-two-dimensional exciton–polariton system in a circular microcavity mesa under the conditions of resonant photoexcitation. It is predicted that a series of transitions from stationary to self-oscillatory and further to chaotic states occurs when several size-quantized sublevels are excited. The transition from stationary states to oscillations is accompanied by the rotational symmetry becoming discrete, while in the chaotic region the spatial symmetry disappears completely. Analogous phenomena in a spinor system result in polarization chaos.</p>