In this paper, a low-profile circularly polarized (CP) patch antenna with high gain and enhanced axial-ratio bandwidth is presented. The antenna is composed of a pin-loaded patch radiator and a probe-fed non-radiative ring resonator. On the one hand, the patch radiator dominates the radiation, and the loading of shorting pins facilitates its high gain due to enlarged radiating area at resonance. On the other hand, the ring resonator with perturbation produces two additional split degenerate modes, which not only widens the bandwidth of magnitude, but also generates the required quadrature phase shift for CP radiation. With these arrangements, attractive features such as stable high gain, improved AR bandwidth and low profile are achieved simultaneously, demonstrating the unique advantages of this technique.