The Newfoundland Royal Naval Reserve was a military reserve force founded in 1900 in what was then the Newfoundland Colony, a part of the British Empire. From 1900 to 1902, approximately 50 members of the reserve trained each winter with the North American and West Indies squadron of the Royal Navy until a steam and sail powered training ship, HMS Calypso, was provided by the United Kingdom in 1902 for local drills before at-sea training with the NA and WI squadron. The reserve had 375 members by late 1903 and then between five and six hundred reservists until the start of World War I, growing to over 1000 in 1915. 1,964 Newfoundlanders served with the Naval Reserve in World War I, suffering 192 fatalities. The Reserve disbanded in 1920-1921. Calypso, having been renamed HMS Briton, was sold as a storage hulk and was burned for salvage near Lewisporte, Newfoundland and Labrador.

The Royal Naval Reserve (RNR) is one of the two volunteer reserve forces of the Royal Navy in the United Kingdom. Together with the Royal Marines Reserve, they form the Maritime Reserve. The present RNR was formed by merging the original Royal Naval Reserve, created in 1859, and the Royal Naval Volunteer Reserve (RNVR), created in 1903. The Royal Naval Reserve has seen action in World War I, World War II, the Iraq War and the War in Afghanistan.