Eggshell powder (ES) inhibitive effect on Type 316 austenitic stainless steel (SS) corrosion in sodium chloride and sulfuric acid solutions was studied using weight loss, linear polarization, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM/EDX) techniques. Experimental observation proves the inhibitor to be effective in both media with inhibition efficiencies of 99.99 and 94.74% owing to the inhibitive action of ES molecules in the chloride and acid solutions. Stainless steel samples in chloride solution have significantly lower corrosion rate values than stainless steel samples in sulfuric acid solution at all concentrations studied. The preferential adsorption of residue ES monomers in the inhibitor decreased the corrosion rate value. Polarization curve measurements show that ES is a mixed type inhibitor for SS corrosion in 0.5 M H2SO4 and 3.5% NaCl solutions. The ES inhibited the SS corrosion in both studied media and its inhibition depends on exposure time, concentration, and environment. Stainless steel ES adsorption follows Langmuir adsorption isotherm. SEM/EDX investigation shows less corroded surface, fewer pits for SS in NaCl/ES solution with slight deduction in the chromium composition percentage, and other alloying elements compared to SS sample in H2SO4/ES solution. The applied techniques explained that ES is an effective inhibitor for Type 316 SS in NaCl solution than in H2SO4 solution. Good agreement between linear polarization and weight loss results was observed.