The Royal Navy has kept a watching brief on the Stirling Engine since 1945. In recent years a more tangible interest has been shown. The development of the Stirling for naval usage has not been a high priority but this could change in the future. In the 1990s existing power plants will need to be replaced and new warships will appear and then the claims of the Stirling will be more closely examined than hitherto. Nevertheless investigative research and development work has been carried out by Royal Navy personnel and for the Royal Navy by defence contractors with the aim of assessing the feasibility of using Stirling machines in a naval environment. This work has enabled a substantial database of knowledge to be established so that in the future the Royal Navy can be an “intelligent customer” if Stirling engines have to be procured. The paper given here details the work carried out on Stirling engines in the Royal Navy over the last ten years.