Bentonites are specific types of clay, commonly formed by weathering of volcanic ash. Bentonites can adsorb more water and other substances than other clays. Because of their unique properties, great abundance, and relatively low cost of exploitation and production, bentonites are used in numerous applications. This publication introduces (data) and discusses a set of 40 bentonite/clay samples from all over the world. It includes compositional and mineralogical data for these samples, making it a valuable reference on bentonite clays worldwide. Finally, the expert authors provide information on the wide range of bentoniteapplications in various fields, which has rarely been compiled in a single volume before.