Plants create far more than the compounds needed for growth. Their secondary metabolites, such as alkaloids, terpenoids, and phenolics, are vital for defense, adaptation, and interaction with the environment. These natural products are equally important to people, providing medicines, nutraceuticals, flavors, fragrances, dyes, and sustainable agricultural solutions. This book introduces the occurrence, structure, biosynthesis, and ecological roles of major secondary metabolites. It explains how plants produce these compounds, how they function in nature, and how they can be applied in health, agriculture, and industry. Aimed at students, researchers, and professionals in plant science, agronomy, and biotechnology, Plant Secondary Metabolites - Occurrence, Structure and Role offers a concise, accessible guide to these remarkable molecules and their potential to address global challenges in food, health, and sustainability.