Ionic liquids are organic salts that are typically in liquid phase when their temperature is below 100 °C (212 °F). They are nonflammable and have very low vapor pressure, which make them environmentally friendly alternative to organic solvents. Chemical reactions with ionic liquids can be more efficient, results in less waste and pollution, lower energy consumption, safer manufacturing processes, and reduced resource usage.This book is focused on ionic liquids and their applications. The book begins by introducing ionic liquids, their structure and properties and their synthesis and characterization methods, next, synthesis methods with ionic liquids are reviewed, and then their industrial applications in various fields and finally emerging developments in the area.