In this book, the authors have given a brief Introduction on gold nanoparticles synthesis, characterization and applications. The language is simple and easily understandable. Various methods for gold nanoparticles synthesis and their advantages and disadvantages were covered. Much emphasis was given for biological synthesis, especially using Actinobacteria. Valuable information was added on factors affecting gold nanoparticles synthesis. The authors further stressed on application of gold nanoparticles in various fields such as cancer therapy, drug delivery, bio-sensing applications, microorganism detection, antimicrobial properties, track phagokinetic and use as a colorant. The book is very useful for the beginners in the field of nanotechnology.