Abstarct: The Ultrasonic Shot Peening (USP) process is recognized as a modern technique for enhancing the mechanical properties of materials and components. In this process, the surface of a component is subjected to severe impacts by shots made of specific materials and diameters, generating compressive residual stresses. The shots move randomly due to the oscillations of a vibrating body (horn) operating at frequencies above 20 kHz, impacting the workpiece's surface multiple times within a set duration. This study examines the effect of the USP on the mechanical properties, corrosion resistance, and mextallurgical characteristics of AISI 316L stainless steel. AISI 316L, an austenitic steel, is widely used in marine, chemical, food, and pharmaceutical industries due to its high corrosion resistance. In this study, the number of shots, peening distance, and shots' diameter and material were kept constant. The peening time and power percentage of the ultrasonic generator were selected as variable input parameters, with upper and lower levels assigned to each. Surface roughness, surface hardness, transverse cross-sectional microhardness, and corrosion characteristics were measured as response parameters. The experimental tests were designed and conducted using the full factorial design (FFD) method. The results indicated that after 45 seconds of USP at 100% power, the arithmetic mean surface roughness increased from 0.96 µm to 1.39 µm. Additionally, a 195-second peening time at 100% power increased the surface hardness from 15.6 HRC to 22.2 HRC. Microhardness was measured at depths of 75 and 250 µm in the transverse cross-section of the specimens. The results showed that at the upper limits of peening time (195 seconds) and power percentage (100%), microhardness increased from 241.33 VHN by 44.37% and 18.5% at depths of 75 µm and 250 µm, respectively. Corrosion tests in a 3.5% NaCl solution indicated that the maximum input parameters decreased the specimen's corrosion resistance from 178500 ohm to 230 ohm. Microscopic images revealed dimples formed due to shot impacts, with increased peening time and power percentage enhancing surface coverage. Statistical analysis of macrohardness, microhardness, and corrosion tests results was performed using the ANOVA, and optimum conditions for achieving desired mechanical properties and corrosion resistance were determined using the desirability method. The study found that the power percentage of the ultrasonic generator significantly affected macrohardness and microhardness, while peening time was the most influential parameter for corrosion resistance. The maximum value of microhardness (21.133 HRC) was achieved with a desirability of 82%, corresponding to a 195-second peening time and 100% power. Optimal microhardness at depths of 75 and 250 µm was determined with a desirability of 87%, corresponding to the upper limits of peening time and power percentage. The suitable corrosion resistance was determined with a desirability of 89%, corresponding to a 45-second peening time and 40% power percentage.