Abstract: The present invention relates to a lithographic apparatus, comprising: —a base frame (10), adapted for mounting the lithographic apparatus (1) on a support surface (9), —a projection system (20) comprising: —a force frame (30), —an optical element (21) which is moveable relative to the force frame, —a sensor frame (40), which is separate from the force frame, —at least one sensor which is adapted to monitor the optical element, comprising at least one sensor (25) element which is mounted to the sensor frame, —a force frame support (31), which is adapted to support the force frame on the base frame, —an intermediate frame (45), which is separate from the force frame, —a sensor frame coupler (41), which is adapted to couple the sensor frame to the intermediate frame, —an intermediate frame support (46), which is separate from the force fame support and adapted to support the intermediate frame on the base frame.