(-)-Guaiol, also known as (-)-Guaiol or Guaiol, is a sesquiterpene alcohol with the molecular formula C15H26O. It is a natural product found in the essential oils of various plants, most notably guaiac wood (Guaiacum officinale) and cypress pine (Callitris species). It exists as a colorless to pale yellow viscous liquid with a characteristic woody, balsamic aroma. This compound is primarily recognized for its pharmacological activities, particularly in the respiratory system. It exhibits significant expectorant and antitussive (cough-suppressing) properties. Research indicates that (-)-Guaiol can help in clearing mucus from the airways and has been investigated as a potential active pharmaceutical ingredient (API) in formulations for treating bronchitis and other respiratory conditions. Its mechanism is thought to involve modulation of respiratory tract secretions and anti-inflammatory effects. Beyond its medicinal use, (-)-Guaiol is also valued in the fragrance and flavor industry due to its pleasant, persistent woody scent. It serves as a fixative and base note in perfumery. As a plant-derived sesquiterpenoid, it is a subject of interest in natural product chemistry and phytochemical research.