A heatsink (2), comprising a heatsink body (3) extending between two endsides (4, 5) of the heatsink body. The heatsink is designed for introducing the heatsink with the first endside ahead into an aperture (16), which is provided in a wall (17), and for a thermal conductive connection of a heat-generating element (14) to the second endside, with a main direction of extent (6) of the heatsink body (3) from the first endside (4) to the second endside (5) being bent or sharply bent. Furthermore, an illumination system with such a heatsink is disclosed.