Recently, the improvement of diode pumping in solid state lasers and the development of double clad fiber lasers have allowed to maintain excellent laser beam quality with single mode fibers. However, the fiber output power if often limited below a power damage threshold. Coherent laser beam combining (CLBC) brings a solution to these limitations by identifying the most efficient architectures and allowing for excellent spectral and spatial quality. This knowledge will become critical for the design of the next generation high-power lasers and is of major interest to many industrial, environmental, defence and scientific applications. The purpose of this book is to present the more recent concepts of coherent beam combining by the world leaders in the field. After a general presentation of laser beam combining and associated challenges, the book will review functionalities and techniques in details with an emphasis on practical implementations. Thus both scientific and engineering aspects are addressed. .