<p>Cymbopogon citratus (lemongrass) extract has been tested as an environmentally friendly corrosion inhibitor against copper in 1 M H₂SO₄ solution through both experimental and computational methods. The corrosion inhibition performance of lemongrass extract on copper has not yet been systematically explored, despite its known effectiveness on carbon steel. The objective of this work is to determine the inhibition efficiency, identify the active compounds responsible for protection, and elucidate the adsorption behavior using Density Functional Theory (DFT) and Monte Carlo simulations. This study was conducted at various inhibitor concentrations, with the maximum inhibition efficiency reaching 97.70% at a concentration of 500 ppm. Lemongrass extract showed the formation of a monolayer by physisorption at room temperature (298&#xa0;K). GC-MS analysis identified the main components of lemongrass extract, namely citral/geraniol (32.48%), Z-citral (28.00%), and trans-geraniol (14.69%). Density functional theory (DFT) studies evaluated the electronic properties of the main compounds of lemongrass extract, including HOMO and LUMO energies, to understand the tendency of molecules to donate electrons to the copper surface. DFT results showed that citral and geraniol were dominant in inhibiting corrosion. Monte Carlo simulations confirmed the stable interaction between the inhibitor molecules and the Cu(111) surface. It reveals that lemongrass extract is a promising plant-based alternative for copper corrosion control with minimal environmental impact.</p> Graphical Abstract <p></p>