Rear Admiral John Saumarez Dumaresq CB, CVO (/dʊˈmɛrɪk/ duu-MERR-ik; 26 October 1873 – 22 July 1922) was an officer in the Royal Navy. He served during the First World War but is most remembered as an inventor, for development of the device named after him, the Dumaresq, which helped users calculate the rate at which the range to an enemy ship was changing over time. He was the first Australian born officer to command the Australian Fleet.