The qualitative and quantitative composition of the essential oils obtained from wild Sicilian rosemary plants ( Rosmarinus officinalis L.) has been investigated. Samples were collected in Sicily after an ideal division of the island into three large areas, namely Val Mazara (M), Val di Noto (N) and Val Demona (D), according to an ancient and historical territorial subdivision of the island. The essential oils were obtained by hydrodistillation and analyzed by GC-FID-MS, identifying 100 compounds representing more than 96% of the oils. Monoterpenes, both hydrocarbons and oxygenated, were the most highly represented components: the former with a range of 21–68% and the latter with a range of 29–79%. On the basis of the results of this study, comprising a cluster analysis, and on the commonly accepted subdivision of rosemary essential oils, namely cineoliferum, verbenoniferum and camphoriferum chemotypes, most of the wild Sicilian rosemary samples must be classified as cineoliferum chemotype.