The invention relates to an optical system of a microlithographic projection exposure apparatus, in particular for operation in the EUV, comprising a mirror arrangement composed of a plurality of mutually independently adjustable mirror elements, and at least one polarization-influencing arrangement arranged upstream of the mirror arrangement relative to the light propagation direction, wherein the polarization-influencing arrangement has a group of first reflection surfaces and a group of second reflection surfaces, wherein the first reflection surfaces are tiltable independently of one another, and wherein, during the operation of the optical system, light reflected at respectively one of the first reflection surfaces can be directed onto the mirror arrangement via respectively a different one of the second reflection surfaces depending on the tilting of the first reflection surface.