A muffler (1) for an exhaust system of an internal combustion engine, especially of a motor vehicle, has a housing (2), which encloses a muffler volume (7) and has at least one flat wall area (6), with at least one inlet tube (3) and with at least one outlet tube (4) and with at least one bracket (5) for fastening the muffler (1) to a holding structure. A lightweight construction is simplified if at least one wall section (11) of such a flat wall area (6) is formed by a flat lightweight panel (12) with sandwich structure.