Furosemide (4-chloro-2-furan-2-ylmethylamino-5-sulfamoylbenzoic acid) was examined as an inhibitor for the corrosion of carbon steel (CS) in 1.0 M HCl. The investigation included mass loss (ML) and electrochemical techniques: potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM). The efficiency of inhibition rises with increasing Furosemide concentration and temperature. At 300 ppm, the IE% reached 90%. This compound's behaviour follows the Temkin isotherm with good fit. The presence of varying quantities of the substance influences both anodic metal dissolution and cathodic hydrogen evolution (i.e., mixed type). Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) were used to detect the effect of this compound on the CS surface. The molecular inhibitory effect of furosemide was demonstrated using quantum chemical calculations, and the molecular simulation results demonstrated the adsorption of these derivatives on the carbon steel surface.