HMS H8 was a British H-class submarine built by the Canadian Vickers Co., Montreal. She was laid down on 19 May 1915 and commissioned in June 1915. Like other Canadian-built submarines, she was sailed across the Atlantic for service in the North Sea and as recognition of this she initially remained under the command of her Canadian captain, Lieutenant-Commander B. L. Johnson, R.N.R. with a largely reserve crew. HMS H8 was sold on 29 November 1921 in Arbroath.