The inorganic membrane reactor is a combined unit operation of chemical reactions and membrane separations. By having a membrane reactor, the downstream separation load can be reduced. Also, the yields can be increased and conversion can be improved for equilibrium limited reactions. However, many of the industrial chemical reactions take place at high temperature that the conventional polymeric membranes cannot withstand. A great deal of research has been done recently to develop ion-conducting ceramic membranes. Many of these have been successfully employed to form membrane reactors for many industrially relevant chemical reactions, such as hydrogenation, dehydrogenation, oxidation, coupled reactions, and decomposition reactions. An overview is given for the area of inorganic membrane preparations and membrane reactors. Many examples of petrochemical interests are presented, including hydrocarbon conversions and fuel cell applications.