A regenerative heat pipe phase-change engine is disclosed, and may include an evaporator, a piston cylinder fluidically coupled to the evaporator, a piston configured to move within the piston cylinder, a condenser fluidically coupled to the piston cylinder, and a closed-loop fluid return system. The evaporator may be configured to absorb external thermal energy and to vaporize a working fluid within the evaporator. The piston may be configured to be driven by pressure exerted by the vapor generated in the evaporator. The condenser may be configured to condense the vapor into a condensate, such that a pressure differential is created between the condensate and the vapor. The closed-loop fluid return system may be configured to transport condensate from the condenser to the evaporator.