Abstract. Benachour H, Ramdani M, Lograda T, Chalard P, Figueredo J. 2020. Chemical composition and antibacterial activities of Capparis spinosa essential oils from Algeria. Biodiversitas 21: 161-169. The essential oils of Capparis spinosa L. collected from six locations in Algeria were obtained by hydro-distillation. The chemical composition of oils was performed by GC-MS. The disc diffusion method is applied for the antibacterial activity. The extraction produced low yield (0.03%). The result of chromatographic analysis (GC/MS) leads to the identification of 33 components; palmitic acid (38.19%), nonanal-n (12.61%), cymene-2,5-dimethoxy-para (8.94%) and octacosane (5.49%) were the major components of these oils. The result of cluster analysis based on essential oils constituents showed the presence of three chemotypes,i.e., the chemotype of Nonanal-n-Cymen 2,5 dimethoxy para-Dodecanal, the chemotype of Nonanal-n-Hexadecanoic acid-tetracosane and the chemotype Tetracosane-n-pentyl furane-2-octacosane. In-vitro antimicrobial activity of caper oils against nine bacterial species showed that the oils have no activity against E. coli and have modest activities against eight other bacterial species tested; however, the desirability test shows that the oils used were not effective on the bacteria tested.