Kilowatt-class fiber lasers are reviewed. From the early days, fiber lasers have been studied to make use of the high pump intensity resulting from light confinement in the fiber core. In a conventional fiber laser, the pump light is coupled through the fiber core end section. This section is too small to launch a high power diode pump beam. This limits the output power to several tens of mW. The double-clad structure allows us to increase the output power by several orders of magnitude but it can hardly exceed of a few tens of W. A new concept called “fiber embedded fiber laser” or“free shape laser” will again increase the maximum output power, making kW fiber lasers a reality. In this paper, this new concept is presented and compared with usual fiber laser technology.