Lavandula species are one of the most useful aromatic and medicinal plants with a great economic value for pharmaceutical, food and flavor industries, cosmetics, perfumery, and aromatherapy. The pleasant fragrance, physiological effects, and commercial significance are due to the their essential oils, with a highly variable composition dependent on the genetic, environmental and processing factors. This paper provides a systematic view on the chemistry of lavender essential oils especially considering the studies in the last 15 years. The review presents the characteristic chemical constituents and chemotypes of seventeen Lavandula species. The intra- and interspecific variability is primarily discussed dependent on the geographic area, onto-and morphogenetic factors, and extraction methods. In addition, biosynthesis of lavender terpenes is presented.