Abstract: A gas discharge laser includes a laser capillary in a tubular glass envelope which has at its two ends reflectors having optical axes which coincide with the axis of the laser capillary and which together constitute a laser resonator. A Brewster window is mounted in the envelope immediately before one of the reflectors. The Brewster window is placed in a holder manufactured from metal sheet material so that one side thereof is pressed against three regions of engagement on the holder whereby no mechanical stresses occur in the Brewster window. These stresses would otherwise disturb the polarizing effect of the Brewster window. This holder can be manufactured with small tolerances and in a very cheap manner.