HMCS St Julien was one of twelve Battle-class naval trawlers constructed for and used by the Royal Canadian Navy (RCN) during the First World War. Following the war the ship was transferred to the Canadian Department of Marine and Fisheries and converted into a lightvessel. Re-designated Lightship No. 22, the ship remained as such until 1958. The ship was sold for commercial use and renamed Centennial and was in service until 1978.

The Battle-class trawlers were a class of naval trawlers built for and used by the Royal Canadian Navy (RCN) during the First World War. Between the wars, some remained in RCN service, but most were transferred to the Department of Marine and Fisheries, where they performed a number of functions, including working as lightships and fisheries patrol vessels. During the Second World War, a number of these trawlers were re-acquired by the RCN, but all the navy's Battle-class trawlers were decommissioned soon after the war. A number of the class remained in civilian government and commercial service for years after the war, although most had been disposed of by the early 1960s.