The inhibitive effects of aqueous Cactus extracts on the corrosion of carbon steel have been investigated; in 3.5% NaClusing polarization measurements. The obtained results show an inhibition efficiency of about 94% in the presence of 1ppm Cactus at 298K. The Cactus extract acts as mixed inhibitor according to the corrosion potentials Ecorr shifted toward either noble or active direction in the presence of inhibitor. The adsorption of used Cactus compounds on the carbon steel surface obeys LangmuirÂs isotherm. Theapparent activation energy, enthalpy of the dissolution process and the free energy were determined and discussed.