Operation of the first supersonic combustor‐driven purely chemical CO laser is reported. The combustor is fueled with NF3‐CH4‐H2‐CS2and produces a mixture of HF, N2, CS, CS2, and S which is mixed with dry air and N2O during a supersonic expansion into the laser cavity. A chain reaction involving CS and O2is initiated by the S atoms and produces CO with a non‐Boltzmann vibrational‐rotational energy‐level population distribution. The laser produces 450 W of closed‐cavity power as determined by mirror calorimetry.