Abstract <p>Sesquiterpenes are a fascinating and significant class of organic compounds with a wide range of practical applications. In this review, we examine representatives of this group of terpenoids, which include acyclic (linear), monocyclic, bicyclic, and tricyclic structures. We highlight the main methods for synthesizing these compounds, describe their physicochemical properties, and outline the primary directions of their application. It is demonstrated that sesquiterpenes can occur as hydrocarbons or contain oxygen functionality, including carboxylic acids, lactones, alcohols, aldehydes, ketones, and epoxides. The extension of the chain, along with an increase in the number of cyclizations and biochemical modifications (such as rearrangements or oxidations), allows for the generation of a diverse array of structures derived from sesquiterpenes. Furthermore, we explore the activity of sesquiterpenes as pheromones and juvenile hormones, analyzing their biological activity. This comprehensive overview underscores the importance of sesquiterpenes in various fields, including pharmacology, agriculture, and biotechnology.</p>