A lithographic apparatus including a projection system configured to project a patterned radiation beam onto a substrate and a fluid confinement structure configured to confine immersion fluid in a localized region between a final element of the projection system and a surface of the substrate. The lithographic apparatus is configured to have a space bounded on one side by a surface of the projection system and/or a component of the lithographic apparatus at least partially surrounding the final element of the projection system, and on the other side by a surface of the fluid confinement structure. The apparatus is configured to increase the humidity of the gas within the space.