HMS Neptune was a Leander class light cruiser which served with the Royal Navy during World War II. Early in 1941 the New Zealand Government responded to an Admiralty request for sailors to man an additional cruiser. Neptune was selected and was expected to leave the United Kingdom for New Zealand in May. However, because of the loss of cruisers during the Crete campaignNeptune was instead attached to Admiral Cunningham's Force K, based on Malta. On 19 December 1941 she was sunk by mines. Only one crewman survived.
150 of those lost were New Zealanders, 80 of them had served in the Naval Reserve before the outbreak of war. The loss of Neptune was the greatest single tragedy New Zealand Naval Forces have experienced.