Abstract: A multi-cycle thermal reciprocating machine of the type commonly known as Stirling engine, which operates on a closed cycle with a compressible fluid as the operational medium. Double-acting pistons are combined into reciprocating members, each of which is in contact with the operational medium of at least four different Stirling cycles. These cycles occur simultaneously and are symmetrically phased, each performed in at least two different expansible chambers at two different temperatures, typically one hot expansion chamber connected to a cold compression chamber through a conduit containing two heat exchangers and one regenerator.