Essential oils of Algerian Ruta montana collected from seven different regions characterized by diverse climatic conditions were investigated for their chemical components, oil yield diversity, antioxidant and antibacterial activities. The lowest (0.38%) and the highest (1.45%) yields in essential oils were observed in samples from Tizi ouzou and Djelfa, respectively. GC-MS and 13C-NMR analyses allowed the identification of forty components representing 87.8â99.2% of the total oils. The main components were 2-undecanone (27.2â81.7%), 2-nonanone (1.9â39.5%) and 2-nonanyl acetate (tr â 24.8%). Based on cluster analysis, two groups were determined, including high 2-undecanone and high 2-undecanone/2-nonanone/2-nonanol acetate groups. Antioxidant activity was evaluated by DPPH and reducing power assays. Samples from Mâsila and Djelfa (semi-arid regions) presented the highest antioxidant activity (IC50 = 49.6 Â± 2.7 and 50.2 Â± 3.3 mg/L, respectively). Antimicrobial activity was tested against eight microbial strains using the agar disc diffusion method. Overall, moderate activity was observed (inhibition zones' diameters â¤18 mm). This variation confirmed the impact of the climatic conditions on yield and chemical composition of essential oils as well as their biological activities.