In this paper, a novel four symbols Finite Dimensional Modulation (4FDM) in three dimensional scheme with polarization diversity is presented that seeks to combine the advantageous features of phase shift-keying and conventional orthogonal modulation. Different from QPSK, the four symbols in 4FDM are allocated in three-dimensional Euclidean space to improve the energy efficiency. In addition, the polarization diversity is attached to the proposed system in order to reduce the waste of bandwidth. Analytical results are obtained for the exact symbol and bit error performance of the 4FDM design in additive white Gaussian channels. By computer simulation, the error probability and bandwidth efficiency of the 4FDM scheme are compared with conventional two-dimensional and orthogonal modulation designs such as PSK, QAM, and FSK.