Chitosan is a partially deacetylated derivative of chitin, a natural polysaccharide extracted from crustaceans, insects and certain fungi. Owing to its unique properties such as biodegradability, biocompatability, biological activity and capacity of forming polyelectrolyte complex with anionic polyelectrolytes, chitosan has been widely applied in the food and cosmetics industry, as well as the biomedical field in relation to tissue engineering, and the pharmaceutical industry relating to drug delivery. This handbook gathers current research from around the globe in the study of chitosan and its applications.