Abstract: A rotating electrical machine is disclosed, the machine comprising a stator comprising a stator core and stator end windings extending out of the stator core, a rotor arranged to rotate inside the stator, a rotor shaft, the rotor shaft having a hollow interior, a coolant circuit for circulating coolant through the machine, and a machine enclosure. The coolant circuit comprises an injection tube arranged to introduce coolant into the hollow interior of the rotor shaft. The rotor shaft is arranged such that coolant exits the hollow interior of the rotor shaft at each end of the machine and is propelled outwards towards the stator end windings. The machine enclosure comprises a passageway for supplying coolant to the injection tube. A coolant distribution channel may be provided for distributing coolant to other parts of the machine to allow the machine to be cooled at multiple locations using the same coolant circuit.