This reprint presents the published papers of a Special Issue titled Antioxidant Activity of Essential Oils, of the journal Antioxidants , MDPI. Obviously, essential oils are a point of huge interest, due to them being rich in bioactive substances (with their recognised antioxidant, immunomodulatory, antibacterial, antiviral, etc., effects) and are also used extensively in the beauty/cosmetic industry, food products, etc. Considering the global trend of "return to nature", both in eating habits/nutrition, and in the adjuvant therapies (implying essential oils) addressed in the case of numerous diseases, and taking into account the interest of the authors who submitted their papers, the current topic can be considered to be of great interest and with increased and promising potential for future research.