A beam combiner for combining at least two light beams (1, 2) into one combined light beam (3), in particular in the beam path of an optical arrangement, preferably of a microscope, is with respect to a flexible beam combination with structurally simple means characterized by an acousto-optical element (4) in which a mechanical wave or sound wave for deflecting or bending light beams can be generated, so that a first light beam (1) entering the acousto-optical element (4) and at least a second light beam (2) entering the acousto-optical element (4) exit the acousto-optical element (4) in a collinear manner as a combined light beam (3). Further, a light source with such a beam combiner is specified.