This study evaluates the corrosion inhibition potential of Psidium guajava (guava) leaf extract on mild steel in 1 M HCl solution. The extract was prepared by aqueous reflux method and characterized for its phytochemical content. Corrosion inhibition was assessed through weight loss measurements and electrochemical methods. Results revealed that inhibition efficiency increased with extract concentration, reaching a maximum of 69.15% at 500 ppm. The extract acted as a mixed-type inhibitor and followed the Langmuir adsorption isotherm, indicating spontaneous physical adsorption. The findings suggest that Psidium guajava extract is a promising eco-friendly corrosion inhibitor for industrial applications.