Essential oil of leaves of Asteriscus graveolens was obtained by hydrodistillation and analyzed by GC, GC/MS and 13C NMR. Twenty-seven compounds were identified amounting to 98.1% of the total oil. This essential oil was characterized by having a high content of oxygenated sesquiterpenes (93.3%) with 6-oxocyclonerolidol 19 (74.9%) and 6-hydroxycyclonerolidol 23 (11.8%) are the major components. The inhibition of the corrosion of mild steel in sulphuric acid solution by Asteriscus graveolens essential oil has been studied using weight loss measurements, electrochemical polarization and EIS methods. Inhibition was found to increase with increasing concentration of the essential oil to attain 82.89% at 3g/L. Polarisation curves revealed that this oil act as mixed type inhibitor with a strong predominance of anodic character. The effect of temperature, immersion time on the corrosion behaviour of mild steel in 0.5M H2SO4 without and with the A. graveolens oil at 3 g/L was also studied. The associated activation energy has been determined. The inhibition was assumed to occur via physical adsorption of the inhibitor molecules on the metal surface. The adsorption of inhibitor onto the mild steel surface was found to be a spontaneous process and to follow the Langmuir adsorption isotherm.