This book emphasizes the atom economy aspect of multicomponent reactions. It describes how this methodology has been applied to several named reactions. Among the “twelve principles of green chemistry”, atom economy addresses ‘synthetic efficiency’. A multicomponent reaction can be defined as an energy, cost, and time efficient method for organic synthesis. Instead of making one or two bonds in a chemical transformation, multicomponent reactions generate several chemical bonds in a single operation. This book presents a series of detailed reaction mechanisms that beautifully illustrate this principle. Multicomponent reactions are widely applied to the preparation of complex and diverse molecular structures in academic and industrial research laboratories. As such, this book is targeted at researchers involved in green organic chemistry.