A static mixer for an exhaust gas system of an internal combustion engine with which at least two different fluid streams are mixed almost homogeneously after a short mixing distance, and with which back-flow effects and pressure losses are avoided, to the greatest possible extent. Due to the placement of flow guide devices, the inclined front sections of which are disposed alternately facing in different directions, and by the configuration and placement of the fluid passage spaces, which are delimited by guide elements, intensive and homogeneous mixing of two different fluid streams is achieved, while avoiding turbulent flows and pressure losses. Mixing of the fluid streams is supported by guide vanes that are disposed on the flow guide elements in the front region of the central center element, and on a frame that delimits the inclined sections of the flow guide elements.