A corvette is a small, maneuverable, lightly armed warship, originally smaller than a frigate and larger than a coastal patrol craft, although many recent designs resemble frigates in size and role. During the Age of Sail, corvettes were smaller than frigates and larger than sloops-of-war, usually with a single gun deck. Almost all modern navies use ships smaller than frigates for coastal duty, but not all of them use the term corvette (from the French corvair) or equivalent. The rank Corvette Captain derives from the name of this type of ship.
Most corvettes and sloops of the 17th century were around 40 to 60 feet (12 to 18 meters) in length and weighed 40 to 70 tons (36 to 64 metric tonnes). They carried four to eight smaller guns on a single deck. Over time vessels of increasing size and capability were called corvettes; by 1800 they reached lengths of over 100 feet (30 m) and weights ranging from 400 to 600 tons (around 365 to 544 metric tonnes). One of the largest corvettes during the Age of Sail was the American ship USS Constellation, built in 1855; at 176 feet (54 m) long, she carried 24 guns. She was so large that some naval experts consider her a frigate, or a sloop-of-war.
During the arms buildup leading to World War II the term "corvette" was almost attached to the Tribal class destroyer. The Tribals were so much larger than and sufficiently different from other British destroyers that some consideration was given to resurrecting the classification of "corvette" and applying it to them. This idea was dropped, and the term applied to small, mass-produced anti-submarine escorts such as the "Flower" class of World War Two.
The first modern corvettes were the Flower class (Royal Navy corvettes were named after flowers, and ships in Royal Canadian Navy service took the name of smaller Canadian cities and towns). Their chief duty was to protect convoys in the North Atlantic and on the routes from the UK to Murmansk carrying supplies to the Soviet Union.
The Flower-class corvette was originally designed for offshore patrol work, and was not ideal as an anti-submarine escort; they were really too short for open ocean work, too lightly armed for anti-aircraft defence, and little faster than the merchantmen they escorted, a particular problem given the faster German U-boat designs then emerging. They were very seaworthy and maneuverable, but living conditions for ocean voyages were appalling. Because of this the corvette was superseded in the Royal Navy as the escort ship of choice by the frigate, which was larger, faster, better armed and had two shafts. However, many small yards could not produce vessels of frigate size, so an improved corvette design, the Castle class, was introduced later in the war, some remaining in service until the mid-1950s.
The Royal Australian Navy built 60 Bathurst-class corvettes, including 20 for the Royal Navy crewed by Australians, and 4 for the Royal Indian Navy. These were officially described as Australian Mine Sweepers, or as Minesweeping Sloops by the Royal Navy, and were named after Australian towns.
The Bird-class minesweepers or trawlers were referred to as corvettes in the Royal New Zealand Navy, and two, the Kiwi and Moa, rammed and sank a much larger Japanese submarine, the I-1, in 1943 in the Solomons.
Modern navies began a trend in the late 20th and early 21st century towards smaller, more maneuverable surface capability. Corvettes have a displacement between 540 and 2,750 tons (550 and 2,800 metric tons) and measure 180–330 feet (55–100 meters) in length. They are usually armed with medium- and small-caliber guns, surface-to-surface missiles, surface-to-air missiles, and underwater warfare weapons. Many can accommodate a small or medium anti-submarine warfare (ASW) helicopter.
Turkey began construction on the first of twelve Milgem class stealth corvettes in July 2005. The lead ship, named TCG Heybeliada, is scheduled to begin sea trials in October 2010. The design concept and mission profile of Milgem is similar to the LCS-1 Littoral Combat Ship of the United States. The first eight ships of the Milgem class will be classified as corvettes, while the last four will be named the F-100 class and will be classified as frigates. The F-100 class will be slightly larger in terms of dimensions and will be equipped with the Mk.41 VLS and ESSM, along with other additional systems for improved multi-role combat capabilities.
The Hellenic Navy currently operates the Super Vita-class ships, which are 580 tons full load. The Hellenic Navy has categorised the class as fast attack missile craft. A similar vessel is the Kılıç-class fast attack missile craft of the Turkish Navy, which is classified as a corvette by Lürssen Werft, the German designer of the ship.
The Indonesian Navy will receive indigenously-designed corvettes, called 104 M corvettes, in 2008. The corvette may be armed with the Chinese C-802 anti-ship missile, already installed in the locally-built FPB 57 class fast patrol boats .