Alvand-class

The Alvand class, originally designated the Saam class, is a series of four frigates commissioned for the Imperial Iranian Navy. Constructed in the United Kingdom by Vosper Thornycroft and Vickers between 1968 and 1972, the vessels are based on the Vosper Mark 5 design. The class received a refit in the United Kingdom shortly before the 1979 Iranian Revolution.

The ships utilize a propulsion system consisting of two Paxman Ventura cruising diesels and two Rolls-Royce Olympus gas turbines. The original British-supplied armament included Sea Killer Mark 2 surface-to-surface missiles and Sea Cat surface-to-air missiles, supported by Plessey air surveillance radar and Contraves Seahunter fire control systems. During the 1990s, the Islamic Republic of Iran Navy modified the armament, replacing the Sea Killer missiles with C-802 anti-ship missiles and substituting the Sea Cat system with an additional anti-aircraft gun. The vessels also received torpedo tubes and mortars during these updates.

The class entered service in 1971 and 1972. Originally named after figures from the Shahnameh, the ships were renamed after Iranian mountains following the 1979 Revolution. The frigates were deployed during the Iran-Iraq War, specifically during the "Tanker War" phase. In April 1988, the class engaged United States Navy forces during Operation Praying Mantis. In this engagement, the Sahand was sunk. Three vessels of the class—Alvand, Alborz, and Sabalan—remain in active service. The Alvand design served as the basis for the subsequent Iranian-produced Moudge-class frigates.