Ionic liquids are a class of compounds composed entirely of ions that exist in the liquid state at relatively low temperatures, typically below 100°C. They are often made up of a bulky organic cation and an inorganic or organic anion. The unique properties of ionic liquids, such as negligible vapor pressure, high thermal stability, and excellent solvating abilities, make them highly attractive for a variety of applications. One of the key advantages of ionic liquids is their tunability. By altering the combination of cations and anions, researchers can design ionic liquids with specific properties tailored for particular tasks. This makes them highly versatile in various fields, including green chemistry, where they serve as environmentally friendly solvents that reduce the need for volatile organic compounds (VOCs). Additionally, ionic liquids are used in electrochemistry for applications such as batteries and supercapacitors, due to their high ionic conductivity and wide electrochemical window. They are also used in catalysis, pharmaceuticals, and advanced material synthesis, where their unique solvent properties can improve reaction rates and selectivity. This book elucidates new concepts and their applications in a multidisciplinary manner. The topics included in this book on ionic liquids are of utmost significance and bound to provide incredible insights to readers. For all those who are interested in ionic liquids, this book can prove to be an essential guide.