Ionic liquids are often portrayed as Green Solvents, however, 'Greenness' can only be measured in the context of the overall process. A perspective on the applications of ionic liquids in Green Chemistry, which focuses on the characteristics of ionic liquids and their contributions to Green Synthesis and Separations processes, followed by an explanation of the objectives and general organization of this book are presented.The recent growth in interest in ionic liquids (ILs), reflected by articles in the scientific and popular press (i) has been driven largely by the perceived opportunities that are presented to effect improvements in industrial processes by using Green principles, driven by increased environmental awareness and the desire for increased process efficiency with associated overall cost savings (2).The basic, fundamental concepts behind both Green Chemistry and Ionic Liquids is not new, however, the growth of interest in ILs and the influence of new minds, new approaches and enthusiasm are generating new solutions and driving changes in industrial and commercial practice, proving that Green Chemistry alternatives exist. Industrial adoption of new methods and practices is, however, ultimately going to be based on cost and demonstration of both viability and significant improvements over current practice. It is essential that ionic liquid processes and technologies can be shown to be better than existing methods.2