In this study, the essential oil composition and antibacterial activity of an underexplored population of Cymbopogon martinii (Roxb.) W. Watson was investigated using GCâFID, GCâMS, disc diffusion and micro dilution broth assay. To substantiate the stability of the essential oil profile, the population was grown in the experimental field and its oil was analysed at different growth stages. Altogether, forty-eight constituents, comprising 91.5â96.8% of the total oil composition were identified. Main constituents of the oil were trans-p-mentha-2,8-dien-1-ol (16.6â22.8%), cis-p-mentha-2,8-dien-1-ol (7.2â9.7%), trans-p-mentha-1(7),8-dien-2-ol (9.8â15.8%), cis-p-mentha-1(7),8-dien-2-ol (11.3â18.0%), limonene (10.5â34.8%), isopiperitenol (3.1â5.0%), trans-carveol (3.5â4.5%) and carvone (2.6â3.6%). The oil exhibited wide spectrum, moderate to very good activity against pathogenic bacterial strains (zone of growth inhibition: 9â25 mm; minimum inhibitory concentration, MIC: 125â500 Î¼g/mL). In conclusion, due to high percentage of monoterpene alcohols, the examined oil demonstrated potent antibacterial activity against both Gram-positive and Gram-negative strains.