The effect of aqueous plant extract of Melissa officinalis as corrosion inhibitor for carbon steel in HCl solution was studied using weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Also, surface analysis was done. The results showed that Melissa officinalis extract is a good corrosion inhibitor for C-steel in HCl. The inhibition was due to the formation of adsorbed layer on C-steel surface obeying Langmuir adsorption isotherm. The inhibition efficiency increases with the increase in the inhibitor concentration. FT-IR spectroscopy observation of the metal surface proved the existence of the adsorbed film on the metal surface.