The design, development, and experimental performance evaluation of a Modified Spherical Solar Still (MSSS) enhanced with reflective mirrors are presented in this study. Its performance is compared with that of a conventional Spherical Solar Still (SSS) under Saudi Arabian climatic conditions. To evaluate thermal behavior, freshwater productivity, energy and exergy efficiencies, and economic viability, experiments were conducted for 15 consecutive days in April 2025. The reflective mirrors significantly increased basin water temperature and evaporation rates, while the spherical geometry allowed for consistent solar radiation capture throughout the day. With a maximum basin water temperature of 64.27 degrees C, the MSSS outperformed the SSS by an average of roughly 4 degrees C. Moreover, the MSSS reports cumulative distillate output of 8.22 L/m2 day, that is 2.1 L higher compared to the standalone spherical solar distiller. The average thermal efficiency increased from 10% (SSS) to 15% (MSSS), while the maximum instantaneous thermal efficiency of the MSSS was 33.86%, much higher than the SSS's 15.80%. In a similar vein, the MSSS outperformed the SSS in thermodynamic performance, with a maximum exergy efficiency of 9.52% and an average of 5%, compared with 8.92% and 3.8%, respectively. Economic analysis showed that the MSSS produced a higher annual freshwater yield (123.30 L vs. 91.50 L) despite having a higher capital cost (USD 117.76) than the SSS (USD 58.82). The MSSS cost USD 0.06670 L- 1, while the SSS cost USD 0.04494 L- 1. Testing of the reflective mirror-assisted spherical solar distiller under the climatic conditions of Saudi Arabia is an explicitly novel approach that provides a pathway for field implementations in water-scarce and desert areas that imperatively demand solar-based desalination technology.