Abstract: A multiple cylinder sinusoidal engine comprising a plurality of piston/cylinder arrangements lying parallel to, and around, a shaft cylinder is disclosed. Mounted in the shaft cylinder is a sine shaft, i.e., a cylindrical shaft having formed in its periphery at least one closed, double wave, continuous, sinusoidal groove. Coupling mechanisms couple the pistons to the sinusoidal groove or grooves of the sine shaft such that reciprocating motion of the pistons causes rotary motion of the shaft. Various air/fuel, exhaust and ignition passageways are provided through the sine shaft (or through the engine block in some embodiments) to allow air and fuel to enter the piston cylinders and exhaust gases to be emitted therefrom, and to allow ignition energy to be applied to air/fuel mixtures, as necessary. In one form, a single igniter is provided. The single igniter is coupled, sequentially, to each piston/cylinder arrangement as the sine shaft revolves.