Negative active material for rechargeable lithium battery and rechargeable lithium battery

Disclosed are a negative active material for a rechargeable lithium battery and a rechargeable lithium battery including the same. The negative active material for a rechargeable lithium battery includes an amorphous silicon-based compound represented by the following Chemical Formula 1. [Chemical Formula 1] SiAH [0002] In Chemical Formula 1, A is at least one element selected from C, N, or a combination thereof, 0 < x, 0 < y, and 0.1 ≤ x+y ≤1.5.