This paper presents a novel on-chip terahertz (THz) MIMO antenna operating at 3.633 THz, designed to meet the demands of emerging 6G networks and Internet of Things (IoT) applications. The antenna integrates graphene ground planes with silicon dioxide (SiO 2 ) substrates on silicon wafers and incorporates Circular Split Ring Resonators (CSRRs) to enhance tunability and performance. Key parameters, such as graphene’s chemical potential and relaxation time, are carefully tuned through electromagnetic simulations, which reveal high radiation efficiency and effective suppression of mutual coupling below − 22 dB. Despite challenges related to conductor behavior at THz frequencies, graphene exhibits favourable conductivity and tunability compared to traditional metals, enabling improved Diversity Gain (DG ≈ 10 dB) and an extremely low Envelope Correlation Coefficient (ECC < 0.01) in a 2 × 1 MIMO configuration. These metrics indicate reduced signal interference and enhanced communication reliability. While physical prototype measurements are ongoing, simulation results demonstrate a scalable, compact, and tunable antenna architecture suitable for next-generation wireless systems, particularly for indoor Wi-Fi and 6G/IoT devices. This work addresses key challenges in THz antenna design and provides insights into graphene’s potential as a high-performance conductive element in the THz band, paving the way for future efficient and adaptive wireless communication technologies.