The interest for studying lanthanum compounds has been growing in recent years due to their attractive properties for industrial and technological purposes. Several applications in different fields have been discovered, such as components in various optical, electrical and magnetic applications, as well as catalytic materials. In this case, they are widely used as catalysts, supports and dopants. As a dopant, lanthanum is often used for stabilising the gamma phase of alumina in catalysts designed for high temperature applications, such as in automotive three-way catalytic process, in combustion for gas turbines and boilers and in hydrocarbon reforming. This book discusses how lanthanum is a very promising dopant for heterogeneous catalysts of different applications.