In certain aspects, imaging optical systems with a plurality of mirrors image an object field in an object plane into an image field in an image plane. In the light path between non-obscured mirrors, imaging rays pass through at least one multiple pass-through region between spaced-apart planes which are arranged parallel to the object plane and/or parallel to the image plane. The imaging optical systems have at least one pupil plane. The pupil plane is arranged outside the multiple pass-through region between the non-obscured mirrors. This can provide an imaging optical system which provides for an easier correction of image errors.