Publisher Summary This chapter reviews the idealized types of reactors used for industrial purposes. The chapter discusses the properties and applications of such reactors in the chemical process industries. A reactor is a piece of equipment in which the feedstock is converted to the desired product. Reactors are chosen such that they meet the requirements imposed by the reaction mechanisms, rate expressions, and the required production capacity. Other parameters that must be determined to choose the correct type of reactor are reaction heat, reaction rate constant, heat transfer coefficient, and reactor size. Reactors that are free of the effect of the macrokinetic properties are classified as: batch isothermal perfectly stirred reactor, batch adiabatic perfectly stirred reactor, semi-batch perfectly stirred reactor, continuous isothermal perfectly stirred reactor flow reactor, continuous adiabatic perfectly stirred flow reactor, continuous isothermal plug flow reactor, and continuous adiabatic plug flow reactor. This chapter also reviews the multiphase reactors such as the fixed and fluidized beds.