The Mackenzie-class destroyer was a class of warship used by the Royal Canadian Navy and Canadian Forces from the 1960s–1990s. Six such ships were envisioned, of which four were completed to this specification. The last two hulls were completed to the post DDH conversion St. Laurent-class design (which included helicopter hangars); they were designated as the Annapolis class instead. The four Mackenzie-class destroyers spent most of their service in the Pacific Ocean, used primarily in a training role. Their only significant update was the DELEX (destroyer life extension) program, which was completed between 1982 and 1985 and updated their navigational radar and their sonar.