This paper presents a dual-band, wideband multilayer rectangular dielectric resonator antenna (RDRA) for beyond-5G (B5G) communication systems. A high-permittivity dielectric resonator is employed for sub-6 GHz operation, while a stacked multilayer dielectric structure enables millimeterwave performance on a common substrate, resulting in a large frequency ratio within a compact footprint. The antenna is excited by simple coaxial probe feeds, ensuring low loss and structural simplicity. Experimental results demonstrate a wide impedance bandwidth 21.4–34 GHz (47.5%), as well as dualband operation at 3.6–3.75 GHz and 35.10–40 GHz. Maximum

measured gains of 5.57 dBi and 6.15 dBi are achieved in the sub-6 GHz and millimeter-wave bands, respectively, with stable radiation characteristics and high radiation efficiency across both bands. These results indicate that the RDRA is a suitable candidate for integrated sub-6 GHz and millimeter-wave B5G applications.