In multifunctional reactors chemical and physical unit operations are carried out simultaneously. Traditionally chemical reaction engineering considers mass and heat transfer processes in combination with chemical reactions. However, the term multifunctional reactor points to an extended and more detailed view of process integration. By application of these reactors it is possible to save investment and/or operating costs, to meet environmentally relevant limits or to improve process safety. Mechanical and thermal unit operations are especially good candidates for integration with a chemical reaction step, In this contribution selected multifunctional reactors are presented, which were either adopted from the literature or are the subject of the authors’ own research activities.