A paraffin-based frequency reconfigurable antenna operating at 100 GHz is reported in this article. Paraffin is a mechanical phase-change material (PCM) that undergoes reversible solid-liquid volumetric change of approximately 15%. In addition, due to its low dielectric loss, this material is suitable for certain electromagnetic applications such as antennas at the millimeter-wave band often defined as 30 to 300 GHz. In this work, paraffin-based micro actuators forming variable capacitors are integrated with a slot antenna structure. Here, paraffin is encapsulated with a dielectric layer and actuated using a Joule heater. A variable capacitor is formed between a metal layer patterned on top of the paraffin and the ground layer. Following multi-physics simulation steps, prototype antennas are fabricated and tested. With a low actuation voltage of 5.4 V, 1.4 $\mu \text{m}$ of displacement and 15.3% change in capacitance are achieved. Actuation and switch off time of the device is found to be 5.7 ms and 1.8 ms, respectively. Performance of the reconfigurable antenna is evaluated through on-wafer probe measurements. The antenna covers the bandwidth of 94.1–104.1 GHz ( $S_{11} dB) and the resonance frequency shift of 6.8 GHz is achieved. Applications of such reconfigurable antenna includes wireless communication, radars, and biomedical imaging. [2020-0180]