An exhaust-gas turbocharger (1) having a compressor (2) which has a compressor housing (3); a turbine (4) which has a turbine housing (5); and a compressor-side and/or turbine-side charge pressure regulating device (6) which has a shut-off element (7) which opens or closes a flow opening (9). The shut-off element (7) is in the form of a slide which is mounted on a guide (8) so as to be longitudinally displaceable along a longitudinal central line (LM8) of the guide (8), and the flow opening (9) is arranged at least substantially at a right angle (α) with respect to the longitudinal central line (LM8) of the guide (8).