A chemical reaction mechanism for methane combustion was developed by a method different in principle from previous efforts that start from detailed chemistry and use steady-state and other approximations. It describes, accurately and with the same parameter set, such different phenomena as flames and high and intermediate temperature ignition. The approach used for chemistry simplification resolves the main features of hydrocarbon oxidation into steps, each with simple kinetic sense, describing thermal decomposition of fuel, true and degenerate chain branching, propagation, termination, and the formation of final products. Rate coefficient expressions for elementary reactions were taken from the literature, while those of generalized reactions were optimized using an automated regression procedure against ignition and flame speed data. The predicted composition and pressure dependences for ignition and combustion of methane and methane-ethane mixtures are in good agreement with experiment.