HMCS Ypres was one of twelve Battle-class naval trawlers constructed for and used by the Royal Canadian Navy (RCN) during the First World War.

The RCN's Battle-class trawlers formed part of the Canadian naval response to Admiralty warnings to Canada about the growing German U-boat threat to merchant shipping in the western Atlantic.

[2] Twelve vessels were ordered on 2 February 1917 from two shipyards, Polson Iron Works of Toronto and Canadian Vickers of Montreal.

[4] They were propelled by a steam-powered triple expansion engine driving one shaft creating 480 indicated horsepower (360 kW) giving the vessels a maximum speed of 10 knots (19 km/h; 12 mph).

[4][a] This was considered to be the smallest gun that stood a chance of putting a surfaced U-boat out of action, and they also carried a small number of depth charges.

[9] For the defence of shipping in Canadian waters in 1918, the entire Battle class was assigned to work out of Sydney, Nova Scotia.

[13] After this incident, the crews of other gate vessels would pretend to make elaborate preparations for a collision every time Revenge visited Halifax.