A high-rate spatially modulated space-time block code (HRSM-STBC) based on golden code is presented in which the spatial constellation (SC) codewords and the core STBC code matrix are designed for two active antennas. In addition to the high rate of the core STBC, the number of SC codewords offered by the HRSM-STBC scheme is the largest as compared to existing schemes that have the same antenna configuration. Consequently, the proposed scheme can provide the highest spectral efficiency to date. To maximize the achievable coding gain and diversity, the optimization of the HRSM-STBC is carried out. Performance advantages of our proposed scheme over its existing counterparts such as STBC-SM, H-STBC-SM, STBC-CSM, and DT-SM are demonstrated.