Tannins are a distinct secondary metabolite of plants that can be found in a variety of natural and synthetic sources. The two fundamental forms of tannins are condensed and hydrolyzable tannins, both of which vary in their chemical structure and application. Condensed tannins are extended flavonoids polymer, while polymers of a glucose centre with numerous catechin derivatives are composed of hydrolyzable tannins. These are a significant but commonly neglected class of natural polyphenols due to their anti-nutritional, mutagenic, and carcinogenic effects, hepatotoxic activity, decreased ability to digest, and are co-promoters of many disorders. But the most advanced research has observed and verified a variety of health potentials, including anti-oxidant, anti-cancer, anti-inflammatory, anti-helminthic, anti-microbial, and anti-allergic properties. Having binding capacity with proteins and other molecules, tannins are extensively used as astringents in cases of diarrhoea, skin bleedings, and transudates, and have a broad range of uses in the pharmaceutical industry, while food applications are confined due to their astringency. This chapter focuses on the biosynthesis, classification, occurrence, chemistry, identification, health effects, as well as toxicology, applications, and acceptable consumption limits of tannins.