This review provides a comprehensive overview of the chemical composition and biological activities of essential oils. Essential oils, primarily composed of terpenes and phenolic compounds, exhibit a wide range of biological activities, including antioxidant, anti-inflammatory, antimicrobial, and cytotoxic properties. These activities are attributed to their chemical structure and the presence of specific compounds such as monoterpenes, sesquiterpenes, and phenolic derivatives. The review highlights the importance of essential oils in various applications, including food and cosmetic industries, and human health. It also discusses the methods for extracting and characterizing essential oils, as well as the factors influencing their composition. Additionally, the review explores the potential of essential oils in cancer chemoprotection, allelopathy, and repellent and insecticidal activities. The authors emphasize the need for further research to optimize the use of essential oils in different domains, considering their potential toxicological effects.This review provides a comprehensive overview of the chemical composition and biological activities of essential oils. Essential oils, primarily composed of terpenes and phenolic compounds, exhibit a wide range of biological activities, including antioxidant, anti-inflammatory, antimicrobial, and cytotoxic properties. These activities are attributed to their chemical structure and the presence of specific compounds such as monoterpenes, sesquiterpenes, and phenolic derivatives. The review highlights the importance of essential oils in various applications, including food and cosmetic industries, and human health. It also discusses the methods for extracting and characterizing essential oils, as well as the factors influencing their composition. Additionally, the review explores the potential of essential oils in cancer chemoprotection, allelopathy, and repellent and insecticidal activities. The authors emphasize the need for further research to optimize the use of essential oils in different domains, considering their potential toxicological effects.