A guided-missile destroyer (DDG) is a destroyer whose primary armament is guided missiles so they can provide anti-aircraft warfare screening for the fleet. The NATO standard designation for these vessels is DDG, while destroyers which have a primary gun armament and/or a small number of anti-aircraft missiles sufficient only for point-defense are designated DD. Nations vary in their use of destroyer D designation in their hull pennant numbering, either prefixing or dropping it altogether.
Guided-missile destroyers are equipped with large missile magazines, with modern examples typically having vertical-launch cells. Some guided-missile destroyers contain integrated weapons systems, such as the United States’ Aegis Combat System, and may be adopted for use in an anti-missile or ballistic-missile defense role. This is especially true for navies that no longer operate cruisers, so other vessels must be adopted to fill in the gap. Many guided-missile destroyers are also multipurpose vessels, equipped to carry out anti-surface operations with surface-to-surface missiles and naval guns, and anti-submarine warfare with torpedoes and helicopters.
Although the French Navy no longer uses the term "destroyer", the largest frigates are assigned pennant numbers with flag superior "D", which designates destroyer.