Abstract: A wideband 8-port multiple-input multiple-output (MIMO) antenna for 5G is proposed. The antenna element is a multi-branch monopole. Its structure can yield multiple modes to cover multiple bands. A folded structure is also employed to achieve antenna miniaturization. To enhance isolation, T-shaped protruded ground structures are designed and embedded between the adjacent antenna elements. The simulated and measured results indicate that the return loss of the proposed antenna is larger than 10 dB in the 3-7.1 GHz band, and the isolation is higher than 15 dB in the 3.3-7.1 GHz band. Benefitting from effective decoupling, the proposed antenna shows distinct radiation diversity characteristic. The envelope correlation coefficient (ECC) of the proposed antenna is close to zero in the targeted sub-6 GHz bands. The calculated peak ergodic channel capacity in an 8×8 MIMO system is 43 bps/Hz, reaching up to 3.74 times of the upper limit for conventional 2×2 MIMO. The proposed 8-port MIMO antenna has good diversity and multiplexing capabilities, and it is competent for high-speed data transmission for the 5G communication in the sub-6 GHz bands.