A turbine generator regenerative braking system may be used to slow or stop a rotating shaft or wheel, wherein energy may be recovered as electricity generated by a turbine generator and stored in batteries, ultra-capacitors, or other storage systems. The turbine generator may be fluid-jet powered, the fluid-jet being provided by at least one hydraulic fluid pump linked to the rotating shaft or wheel. A braking actuation system operatively connects/starts the pumping action, and controls may be provided to adjust the flowrate through the fluid-jet nozzle. In some versions of the system, a hydraulic pump, a clutch, and an adjustable-flow nozzle will be dedicated to each ground engaging wheel of the vehicle. In a vehicle, braking is preferably initiated by the driver by actuation of a brake master cylinder that provides hydraulic pressure to cause each hydraulic pump to engage with its corresponding pump. The pressurized fluid output of each pump is then fed to the turbine through the adjustable-flow nozzle. Energy recovery may be optimized by adjusting the direction of the nozzle spray or the location of the nozzle, and/or by providing a multi-stage turbine.