A separator for a rechargeable lithium battery includes a substrate; and a coating layer positioned on at least one side of the substrate, wherein a thickness ratio of the coating layer relative to the total thickness of the substrate and the coating layer ranges from about 5% to about 50%, and a loading level of the coating layer ranges from about 1.4 g/m2 to about 9.8 g/m2, and a rechargeable lithium battery including the same is provided.