This paper has proposed a plasmonic multi-ring structure for an antenna that aims to be deployed in 6G-enabled wireless body area networks (WBANs) for personalized healthcare. Due to their nanoscale dimensions, plasmonic antennas are suitable for integration into ultra-compact wearable sensors and implantable devices used in WBANs, allowing data transmission and continuous health monitoring without sacrificing convenience or portability. The multi-ring type antenna design is a prominent wideband antenna design technique that consists of multiple concentric ring elements made of conductive material, arranged in a planar configuration. The proposed concentric multi-ring antenna structure for terahertz applications is designed with the help of a CST tool, and its features are analyzed. The proposed antenna structure resonates at a frequency of 5.75 THz, with a minimum S11 of −18 dB. It also achieved a bandwidth of 20.27% between 5.23 THz and 6.41 THz. Its dimensions in the micrometer range make it suitable for use in wearable or implanted WBAN nodes.