An illumination system (1) for a microscope, in which a first light source (2), a collector lens (3), an aperture diaphragm (4), and a condenser lens ((5) are arranged in the illumination beam path (6), is described. The illumination light is directed through the aperture diaphragm (4) via the condenser lens (5) into the object plane (9). Arranged in the illumination beam path (6) on the optical axis (20) is a second light source (8) that is imaged at infinity by the condenser lens (5).