Abstract: A high-power flowing-gas laser comprises a laser channel folded to include at least two legs angularly disposed to each other in a common plane and having a single folding mirror between them such that the laser rays through one leg, on the upstream side thereof with respect to the gas flowing transversely across that leg, are reflected by the folding mirror so as to be transposed to the downstream side of the other leg with respect to the gas flowing transversely across the other leg. A number of embodiments are described wherein the laser channel is folded to include four or other even number of legs according to a polygonal configuration, there being a separate flowing gas channel for each leg, all the gas channels directing the gas flow radially inwardly to a common collection region. Among the advantages provided by the described constructions are compensation for phase distortion and amplitude variations, and maximum laser channel length and laser output for a given system size and volume.