A three-dimensional constellation-basedM-ary differential chaos shift keying modulation system, referred to as3D-M-DCSK system, is proposed in this paper. In particular, we exploit the excellent cross-correlation properties of chaotic signals to intelligently combine the 3D constellation mapping and the DCSK scheme, thus increasing the minimum Euclidean distance (MED) between the adjacent mapped symbols. In this way, the date rate and transmission reliability of conventional two-dimensional constellation mapping can be effectively improved. The theoretical expressions for the symbol error rate (SER) of the proposed 3D-M-DCSK system are derived under the additive white Gaussian noise (AWGN) channel as well as the multipath Rayleigh fading channel. Additionally, the peak-to-average-power-ratio (PAPR) performance of the proposed 3D-M-DCSK system is carefully analyzed. Simulation results show that the proposed 3D-M-DCSK system achieves outstanding improvement in terms of transmission reliability and PAPR performance compared to the state-of-the-artM-DCSK system in both AWGN and multipath Rayleigh fading channels.