Multiphase reactions may vary from very slow to very fast, endothermic to highly exothermic. Based on the reaction characteristics, different types of multiphase reactors are used in industrial practice. Multiphase reactors can be broadly classified in two categories: gas dispersed in liquid and liquid dispersed in gas. This chapter explains the criteria that may be applied for selecting a multiphase reactor for a given application. Reactions involving solids or reactions that generate solids must necessarily be carried out in a multiphase reactor that has no clogging problems. Multiphase reactors that have a rotary part requiring sealing need careful maintenance. The chapter provides some examples of large-scale applications of multiphase reactors. Sparged and stirred reactors provide good mass transfer, and their relative merits are discussed here.