<p>The development of emerging technologies in satellite communications, military applications, scientific research, short-range wireless networks, 5G, and mm-wave machine-to-machine communications always demands ultra-high speed transmission capabilities (high data rates), wide bandwidth, high-gain, and low-latency antennas. To achieve these requirements, a high-gain circular quasi-fractal antenna for advanced 5G communications and mm-waves is analysed, fabricated, and investigated. The super-compact (6127 × 6284 µm²) reduced electrical length patch antenna is fabricated on a low-loss RT Duroid 5880 substrate of thickness 127&#xa0;μm at U-band 50&#xa0;GHz frequency. The proposed design utilizes the same concept of a fractal, but it is designed to reduce the electrical length of the antenna patch in reverse-fractal ways. This helps to miniaturize the antenna size to 35.155% and, therefore, the antenna becomes more economical. A two-iteration quasi-fractal is applied to the rectangular patch to minimize the lower current portion from the patch. This results in antenna tuning at 50&#xa0;GHz, enhancing bandwidth and gain values. The antenna achieves a gain of 7.44 dBi and a wider bandwidth from 42.04&#xa0;GHz to 57.34&#xa0;GHz. Therefore, the designed antenna is suitable for wireless personal area networks (WPAN), future LAN, and energy launchers in U-band microstrip to rectangular waveguide transition. A lumped-element electrical equivalent R, L, C circuit of the antenna is generated and validated using the Advanced Design System (ADS) software, and its reflection coefficient (S₁₁) is found in excellent agreement with the S₁₁ of the HFSS-designed antenna.</p>