RationaleThe carbon, hydrogen and oxygen stable isotope composition (δ¹³C, δ²H, and δ¹⁸O values) of plants and their products is linked to photosynthetic fractionation, environmental factors and agricultural practices. Therefore, they contribute to determining the purity of commercial vegetable oils and may provide information on their geographical origin.MethodsMaize, olive, sunflower, groundnut, soybean and rice oils differing in sites of growth in the southern and northern hemispheres were characterized by bulk oil stable isotope ratios (δ¹³C_bulk, δ²H_bulk, and δ¹⁸O_bulk values), fatty acid (FA) concentrations and δ¹³C_FA values using elemental analysis/isotope ratio mass spectrometry, gas chromatography/mass spectrometry, gas chromatography/flame ionization detection and gas chromatography/combustion/isotope ratio mass spectrometry. Principal component analysis was applied to examine the inherent structure of the data.ResultsThe δ¹³C_bulk values of maize oils (−18.4 to −14.9 ‰) are typical for C₄ plants, and those of olive (−30.2 to −28.2 ‰), sunflower (−30.2 to −29.2 ‰), groundnut (−29.3 ‰), soybean (−30.6 ‰), and rice (−34.5 ‰) oils are typical for C₃ plants. The δ²H_bulk values vary from −161 to −132 ‰ for maize oils and −171 to −109 ‰ for C₃ oils. The δ¹⁸O_bulk values of all oils vary between 15.2 and 38.9 ‰. The major δ¹³C_FA differences (>5 ‰) within plant species render the inter‐C₃‐species comparison difficult. These differences are explained in terms of variations in the lipid biosynthetic pathways and blend of vegetable oils of different FA composition and δ¹³C_FA values. The samples from the southern hemisphere are generally enriched in ¹³C compared with those from the northern hemisphere. Differences between the southern and northern hemispheres were observed in δ²H (p < 0.001) and δ¹⁸O_bulk (p = 0.129) values for all C₃ oils, and in δ¹³C_18:1 (p = 0.026) and δ¹⁸O_bulk (p = 0.160) values for maize oils.ConclusionsThe results of this study show that combining bulk and molecular stable isotope ratios, FA compositions and their statistical analysis helps the characterization of the geographic origin of oils. This methodology can be used to detect and source impurities in valuable vegetable oils commercialized worldwide. Copyright © 2016 John Wiley & Sons, Ltd.