Laser resonator, particularly for carbon dioxide lasers, with two resonatornd mirrors having active material between two fully reflecting end mirror faces, which form an unstable resonator cavity, and with at least one third, completely reflecting mirror face reflecting the laser radiation prior to its coupling out through a coupling-out opening of the resonator. So that the laser only requires a reduced degree of coupling out and/or has an improved beam quality, it is constructed in such a way that, in addition to the unstable resonator cavity, between the two end mirrors is provided at least one stable resonator cavity and that the stable resonator cavity is made from the same active material of the third mirror face as the face of one of the two end mirrors with the face of the other end mirror.