In this study, a terahertz dual-band–high-gain, multi-input–multi-output (MIMO) antenna with two and four input ports was realized, with gain values of up to 7.16 dBi and 6.44 dBi, respectively. This represents an increase in gain of 102.4% and 81.8%, respectively, compared to single-input port antennas. By calculating and analyzing the voltage standing wave ratio (VSWR), gain, envelope correlation coefficient (ECC), and diversity gain, the two MIMO antennas achieved perfect impedance matching at their resonance points. Moreover, the interference between the elements of the MIMO antenna was small, and an isolation effect between the units was realized. These MIMO antennas can achieve multiple input signals to regulate the antenna radiation performance and improve signal strength and quality. In addition, they possess good development prospects for achieving high-speed data transmission in the terahertz band and in mobile communication. [ABSTRACT FROM AUTHOR]