HMS H3 (Lt G E Jenkinson) HMS H3 was one of a group of ten H Class submarines ordered in the emergency war programme of November 1914 and built, using American supplied components, at the Canadian Vickers yard at Montreal. She was laid down on 11 January 1915 and was commissioned on 3 June 1915. After commissioning she crossed the Atlantic from St. John’s, Newfoundland to Gibraltar escorted by the armed merchant cruiser HMS CALGARIAN. She was accompanied by H1, H2 and H4.

HMS H3 was mined in the Gulf of Cattaro, Adriatic on 15 July 1916 in the outer defensive minefield off Cattaro, in the Adriatic, and was lost with All Hands.