Tannins are a versatile group of biomolecules whose main role is to protect plants against insects and fungi. From the literature, it is possible to identify several biological properties applicable to the food, animal feed, pharmaceutical, and medical industries. The diversity of its chemical activities and their variety of forms make them suitable for a very wide range of applications. Due to their high chemical reactivity, high availability in raw and plant materials, and easy and environmentally safe extraction, they are widely used in the food, leather, and chemical industries. Examples of current applications include their use in the production of anticorrosive primers as “green and safe” alternatives to synthetic polyphenols for the production of wood adhesives and particle boards. The objective of this book is to present the most updated information related to tannins, their influencing factors in plants, pharmacology properties, potential applications in human and animal-feed health, and the current perspectives of their application in industry.