A regenerator for use with a liquid in a Stirling cycle heat engine is described. Because of the thermophysical characteristics of liquids, such a regenerator can be nearly ideally effective and has thermal properties that can be calculated directly without resort to empirical information. The regenerator described here is designed to minimize loss arising from three sources: thermal conductivity along the regenerator, viscous heating in the working fluid, and imperfect thermal contact between the working fluid and the second thermodynamic medium in the regenerator. Measurements using liquid propylene as a test fluid in the regenerator confirm the design calculations.