Essential oil from aerial parts of Artemisia herba-alba from Morocco was hydrodistilled and its chemical composition oil was investigated by capillary GC and GC/MS. The major components were 1,8-cineole (35.6%) and camphor (24.1%). Artemisia herba-alba essential oil AHAO was tested as corrosion inhibitor of stainless steel (SS) in 1M H3PO4 using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy measurements (EIS) and scanning electronically microscopy (SEM) studies. The results obtained showed that the essential oil of Artemisia reduces the corrosion rate. Tafel polarization method indicates that the plant extract behaves as a mixed type inhibitor. The inhibition efficiency increased with inhibitor concentration to attain 88% at 1 g.L−1 of oil at 298 K. Nyquist diagrams obtained from impedance studies provide results confirming the anti-corrosion effect of the studied plant. The temperature effect on the corrosion behavior of (SS) in 1M H3PO4 without and with AHAO at 1 g.L−1 was studied in the temperature range from 298 to 353 K. Thermodynamic parameters suggested that the adsorption is spontaneous and exothermic process and support physical adsorption mechanism. The experimental data fits well into the Langmuir adsorption isotherm model. SEM/EDS studies provide the confirmatory evidence for the protection of (SS) by the green inhibitor. The results obtained from these methods used are in good agreement.