An augmented reduced mechanism (ARM) for methane combustion has been developed from the detailed mechanism of Glarborg and co-workers (reported in 1998) that was formed by 447 elementary reversible reactions and 65 chemical species. First, an intermediate state of reduction, the skeletal mechanism, is reached by means of sensitivity analysis and reaction-rate analysis. After that, a systematic method for reducing mechanisms based on the steady-state hypothesis and the partial equilibrium assumption is used. The reduced mechanism is obtained via an algebraic procedure. This mechanism consists of 18 lumped reaction steps and 22 chemical species. Both the skeletal and reduced mechanisms are validated by comparison with the results predicted by the detailed mechanism for the main species in methane combustion (CH4, CO, and CO2) in a wide range of operating conditions and generally show good agreement.