PFS-Pro is a state of the art Yb:YAG laser system that provides a unique combination of average power, pulse energy and pulse duration and will be the driving laser for new high repetition rate X-ray sources. It tackles the challenge of third generation laser systems to provide pulses with multi-terawatt peak powers and kilohertz repetition rate using established thin-disk technology and a novel nonlinear broadening scheme. PFS-Pro consists of a chirped pulse amplifier that increases the pulse energy of a commercial fiber laser by a factor of more than 30 million. To this end the pulses originating from the fiber oscillator are stretched in time and coupled into a thin-disk regenerative amplifier to finally obtain an output energy of more than 100 mJ with a kHz-scale repetition rate. Two 4 kW 969nm diode laser stacks provide the pump power for the thin-disks making this amplifier one of the strongest amplifiers of its kind.