An illumination optical unit for projection lithography for illuminating an object field, in which an object to be imaged can be arranged, with illumination light has a field facet mirror having a plurality of field facets. A pupil facet mirror of the illumination optical unit has a plurality of pupil facets. The pupil facets serve for imaging the field facets respectively assigned individually to the pupil facets into the object field. An individual mirror array of the illumination optical unit has individual mirrors that can be tilted in driven fashion individually. The individual mirror array is arranged in an illumination light beam path upstream of the field facet mirror. This can result in flexibly configurable illumination by the illumination optical unit, this illumination being readily adaptable to predetermined values.