The King Sejong the Great class destroyers (Sejongdaewang-geup Guchuk-ham or Hangul/Hanja: 세종대왕급 구축함/世宗大王級驅逐艦), also known as KDX-III, are guided missile destroyers of the Republic of Korea Navy. The lead ship was launched 25 May 2007, sponsored by Kwon Yang-sook, the First Lady of the Republic of Korea; the wife of the Late President Roh Moo-hyun at the time and was commissioned in December 2008. The second ship was commissioned in August 2010. As of 2010, the ROK Navy has committed itself to deploy three ships with an option for three more.
On April 20, 2007, Chief of Naval Operations of the Republic of Korea Navy announced that the lead ship of KDX-III class destroyers will be referred as the Sejong the Great. Sejong the Great (Hangul/Hanja: 세종대왕/世宗大王) is the fourth king of the Joseon Dynasty of Korea. He is credited with the creation of the Korean alphabet, Hangul. The ship features the Aegis combat system (Baseline 7 Phase 1) combined with AN/SPY-1D multi-function radar antennae.
The King Sejong the Great class is the third phase of the Republic of Korea Navy's Korean Destroyer eXperimental (KDX) program, a substantial shipbuilding program, which is geared toward enhancing ROKN's ability to successfully defend the maritime areas around Korea from various modes of threats as well as becoming a blue-water navy. At 8,500 tons standard displacement and 11,000 tons full load, the KDX-III Sejong the Great destroyers are by far the largest destroyers in the Republic of Korea Navy, and built slightly bulkier and heavier than Arleigh Burke class destroyers or Atago class destroyers to accommodate 32 more missiles. KDX-III are currently the largest surface warfare ships to carry the Aegis combat system.
King Sejong the Great class destroyers' main gun is the 127mm/L62 Mk. 45 Mod 4 naval gun, an improved version of the same gun used on other warships from several foreign nations. Point-defense armaments include one 30 mm Goalkeeper CIWS and a RIM-116 Rolling Airframe Missile Block 1 21-round launcher, the first Aegis platform to carry RAM. Anti-aircraft armament consists of SM-2 Block IIIA and IIIB in 80-cell VLS. Anti-Submarine Warfare armaments consists of both K-ASROC Hong Sang-eo (Red Shark) anti-submarine rockets and 32 K745 LW Cheong Sang-eo (Blue Shark) torpedoes. Anti-ship capability is provided by 16 SSM-700K Hae Seong (Sea Star) long-range anti-ship missile, each with performance similar to the U.S. Harpoon. Land-attack capability is provided by the recently-developed Hyunmoo IIIC (Guardian of the Northern Sky) cruise missile, which is similar to the U.S. Tomahawk.
King Sejong the Great class destroyers' are often compared to Arleigh Burke class and Atago class because they utilize the AN/SPY-1 multi-function radar, have similar propulsion and capabilities. One notable difference between the Sejong the Great-class ships and Burkes is the number of VLS cells. Destroyers of the Sejong the Great class will have a capacity of 128 missiles, as opposed to 96 on the Arleigh Burke class (although ships in the Arleigh Burke class has the capability to quad-pack 4 ESSM missiles into one launch cell, greatly increasing armament) and the Japanese Atago class destroyers. The Sejong the Great class is thus one of the most heavily armed ship in the world second only to Kirov class battlecruiser with 352 missiles. Another similarity to Arleigh Burke class Flight IIA and Atago class destroyers is the presence of full facilities for two helicopters, a feature missing from earlier Arleigh Burke and Kongō class destroyers.
Three of these destroyers have, according to South Korean news agency Chosun Ilbo, the capability to "track and monitor any missile launched from anywhere from the North." This capability was demonstrated by the tracking of a North Korean Missile in April 2009.