A lithographic apparatus is described, the lithographic apparatus comprising: an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a projection system configured to project the patterned radiation beam onto a target portion of a substrate, a stage assembly comprising: a substrate table constructed to hold the substrate; and a positioning device configured to displace the substrate table relative to the projection system; a base frame onto which stage assembly and the projection system are mounted; the base frame comprising a first portion configured to support the stage assembly and a second portion configured to support the projection system, the first portion and the second portion being connected to each other via a compliant portion of the base frame.