Aspects of embodiments of the present disclosure provide an electrolyte for a rechargeable lithium battery, and a rechargeable lithium battery including the same. The electrolyte includes a non-aqueous organic solvent, a lithium salt, and additive represented by Chemical Formula 1: In Chemical Formula 1, X1 is CH or a nitrogen atom (N), and Ra is a substituted or unsubstituted alkyl group. The additive may decompose under reducing voltages on the surface of the negative electrode to thereby form a polysulfonate-based passivation film to suppress or reduce gas generation and battery swelling.