HMCS CH-15 was a H-class submarine originally ordered for the Royal Navy as H15 during the First World War. Constructed in the United States during their neutrality, the submarine was withheld from the Royal Navy until after the US entry into the war. Entering service at the very end of the war, the submarine saw no action and was laid up at Bermuda following the cessation of hostilities. The British government gave the submarine to Canada in 1919, and it was in service with the Royal Canadian Navy from 1921 to 1922 as CH-15. The submarine was sold for scrap and broken up in 1927.

The British H-class submarines were Holland 602 type submarines used by the Royal Navy. The submarines constructed for the British Royal Navy between 1915 and 1919 were designed and built in response to German boats which mined British waters and sank coastal shipping with ease owing to their small size. The H class was created to perform similar operations in German waters, and to attack German submarines operating in British waters.