A filter housing (11) has at least one inlet (15) and at least one outlet (17) for the fluid. The filter element (10) includes an open filter bellows (16) of a filter medium (18).The filter element (10) is arranged in a filter housing (11) separating the at least one inlet (15) from the at least one outlet (17). An element axis (14) of the filter element (10) and a housing axis (25) of the filter housing (11) can be aligned parallel or axially to an installation direction (12) of the filter element for installing the filter element (10) into the filter housing. The filter element (10) includes at least one guide crosspiece (46, 48) which extends axially and radially outward on a peripheral exterior side (26), relative to the element axis (14), of the filter element (10). The filter element (10) has at least one seal (42) running peripherally relative to the element axis (14), the seal (42) having a seal line with at least one convexity (54) arranged peripherally between two corner regions of the filter element (10) and is separated by these corner regions.