In this work, a cubic step-up DC-DC converter (C3SUC) is configured in three stages to achieve high gain with reduced voltage stress on the switching elements. Also, the proposed topology highlights the feature of providing continuous input current and establishing a common ground between the input and output. Additionally, the proposed work offers an extremely high voltage gain while enabling the switches to operate at a lower duty ratio, resulting in improved efficiency. A detailed comparative description of works related to the state-of-the-art of high-gain topologies is presented. Moreover, the operating modes, small-signal modeling for stability, practical voltage gain, and efficiency as a function of duty cycle and various power levels of the proposed converter are presented. Further, a hardware prototype with a 300 W power rating and a 400 V output voltage has been implemented in the laboratory. The results obtained are in line with the theoretical findings, exhibiting a peak efficiency of 96.2% and a voltage stress of switching devices lower than the output voltage. For validation, the microcontroller TMS320f28379D is used to test the converter in both open-loop and closed-loop modes, yielding satisfactory results under the dynamic changes applied to the proposed cubic converter.