Ensuring the olive oil quality and authenticity has become a great importance for both traditional and emerging olive oil producing countries. The chemical composition in olive oil heavily varies depending on the olive cultivar and its growing region, the agronomic applications, the olive oil production methods and the process and storage conditions. With the help of some analytical techniques and data evaluation methods, it is possible to grade olive oils in terms of their differences. This research examines particularly fatty acid composition of commercial olive oils (2017/2018 season) with mass detector coupled with gas chromatography (GC/MS). Results were evaluated for grading of them according to IOC regulations based on cultivar (ripe or unripe Ayvalik and Memecik), production (organic, stone mill, cold press, two or more centrifugation systems, filtered or unfiltered) and packing type (transparent or dark glass bottle and plastic bottle), and also their geographic origin (Ayvalik and Edremit towns, the Cunda Island, North Aegean region or South Aegean Region). According to overall data processing, virgin olive samples could be successfully distinguished in terms of theirs geographic origin and cultivar roots. Moreover, it was also explained that the effect of process and package type for grading of olive oils as ‘extra virgin’ or ‘virgin’.