A lithographic apparatus comprises an illumination system for providing a projection beam of radiation. A support structure is provided for supporting a patterning device, the patterning device serving to impart the projection beam with a pattern in its cross-section. A substrate table holds a substrate, while a projection system projects the patterned beam onto a target portion of the substrate. The illumination system comprises a field defining element arranged to define an illuminating field in the plane of the patterning device or in a plane conjugate thereto, the field being off-axis with respect to the optical axis of the illuminating system.