Isolated from mushrooms in 1811 by Braconnot, chitin is the first polysaccharide identified by man, preceding cellulose by about 30 years, while its deacetylated derivative was discovered by Rouget in 1859. In 1894, Hoppe-Seyler confirmed that the product was deacetylated chitin and named it chitosan.

Since, these biopolymers, in particular chitosan, have considerably attracted the interest of scientists and industries in different disciplines including health science, agriculture, chemistry, biochemistry, and environment. The main reasons for this growing interest are its intrinsic biological properties and its versatility as biomaterial.

Today, chitosan continue to offer new horizons to scientists and industrials with a wide range of possible modifications and forms. In this chapter, we aim to present an overview of the state of the art in the applications of chitosan, based on a substantial number of relevant references published in the last two decades on various biological, biotechnological, chemical, and physical topics for both academic and industrial applications.

Of course, this is an ambitious project and the examples discussed in this chapter are not exhaustive but clearly demonstrate the benefit of chitosan in many fields. .