The Friction Stir Welding (FSW) is a latest process of Advanced Welding Technology and was invented in 1991 by The Welding Institute (TWI) at Cambridge, in United Kingdom. In 1995, Friction Stir Welding has been used in production applications by introducing welding of extrusions to form paneling for marine applications in Europe and USA. Since then, the process has been commercialized in many other applications including rail car, automotive, aerospace, heavy truck, medical applications, etc. In this book a detailed emphasis is given about historical developments, types of welding processes, working principles of friction stir welding, design feature of FSW tools, processing on aluminium alloys and application in various industries. Author has also tried to place the opinions of researchers as to what they say about the latest techniques of Friction Stir Welding.