The invention proposes a cooling system (42) for a gas turbine (1), with an annular duct extending axially in the compressor (5). In the annular duct, a ring (15) of compressor guide blades (14, 28, 33) and a ring (17) of moving blades (16) fastened to a rotor disk (19) of the rotor (3) are provided, with at least one cooling-air extraction point (34), arranged on the rotor (3), for diverting a cooling-air stream into a cooling-duct system arranged in the rotor (3), and with a turbine unit (8), in which, when the gas turbine (1) is in operation, components subjected to thermal stress by a hot gas (20) can be cooled by the divertible cooling-air stream, and also with a feed line (46) for feeding a liquid (45) into the cooling-air stream. In order to make it possible to feed a liquid into the cooling-air stream simply and cost-effectively, the invention proposes that the feed line (46) extend with a subduct (44) through at least one of the compressor guide blades (28, 33) of the ring (15), and the orifice (48, 49) for the outlet of the liquid (45) be connected in the region of the cooling-air extraction point (34).