A hydraulic camshaft adjuster (1) with a stator (2) in which a rotor (3) is rotatably arranged. A vane (4) which protrudes radially outwards is provided on the rotor (3), the vane being provided with a pressure chamber delimiting side (7). A pressure chamber supply groove (10) is arranged so as to extend on a separation plane which separates the rotor (3) into two halves in order to supply a hydraulic medium to a pressure chamber formed by the rotor (3) and the stator (2), the pressure chamber supply groove (10) having an outlet (11) in the pressure chamber delimiting side (7) of the vane (4).