HMCS Grilse was a commissioned patrol boat of the Royal Canadian Navy during the First World War.

Launched in 1912 as the private yacht Winchester of the American industrialist Peter Rouss, the vessel was constructed along the lines of a contemporary Royal Navy torpedo boat destroyer.

[3] Constructed for Peter Rouss the son of an industrialist, the yacht was built by Yarrows Shipbuilding at their Scotstoun yard in Glasgow, Scotland.

The American government discovered the sale and attempted to block the transaction, but Ross managed to get out of the country with the ship.

[1] Grilse was commissioned as a torpedo boat on 15 July 1915 with Ross in command and operated off Canada's east coast for much of the war.

Her intended use as the most powerful Canadian warship on the east coast following the laying up of the cruiser HMCS Niobe, was as the primary offensive unit to any sighting of enemy ships.

In December 1916 the ship was sent to the Royal Naval Dockyard in the Imperial fortress colony of Bermuda to join the North America and West Indies Station, but encountered a heavy storm on the way and nearly sank.

[3] Attempts to sell Grilse as surplus in 1920 were unsuccessful, and she was used for training purposes in 1921–22 before being sold to Solomon Guggenheim in 1922.

[9][10] The United States Coast Guard ordered the wreck removed and Guggenheim transferred ownership to a salvage company.