Abstract The chemical composition of the essential oil obtained from Teucrium alopecurus De Noé, an endemic limited to Matmata (southern Tunisia) was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS). Fifty-seven components were identified; the predominant compounds of the oil of Teucrium alopecurus were mainly sesquiterpenes hydrocarbons (61.3%) and oxygenated sesquiterpenes (26.9%); δ-cadinene (13.4%), nerolidyl acetate (12.3%), α-humulene (12.3%), α-guaiene (10.3%) and β-caryophyllene (8.2%).