The negative active material for a rechargeable lithium battery of the present invention includes a carbonaceous material and a silicon-based compound represented by Formula 1: Si.sub.(1-y)M.sub.yO.sub.1+x(1) where 0.ltoreq.y.ltoreq.1, -0.5.ltoreq.x.ltoreq.0.5, and M is selected from the group consisting of Mg, Ca, and mixtures thereof.