Sejong the Great-class (KDX-III)

The Sejong the Great-class, designated KDX-III, is a series of guided-missile destroyers operated by the Republic of Korea Navy. The class represents the third phase of the Korean Destroyer eXperimental program and was developed to enhance maritime defense and support blue-water naval operations. Construction of the vessels has been conducted by Hyundai Heavy Industries and Daewoo Shipbuilding & Marine Engineering. The class succeeded the Chungmugong Yi Sun-sin-class and is scheduled to be followed by the KDDX-class destroyer.

The class is divided into Batch I and Batch II configurations. Batch I vessels utilize the Aegis Combat System Baseline 7 Phase 1 integrated with the AN/SPY-1D(V) multi-function radar. Batch II vessels are equipped with Aegis Baseline 9.C2, which provides integrated air and missile defense (IAMD) capabilities and supports the use of SM-3 interceptors. Sensor systems across the class include the DSQS-21BZ-M hull-mounted sonar, the SQR-220K towed array sonar system, and the Sagem Infrared Search & Track (IRST) system. Electronic warfare and decoy requirements are met by the LIG Nex1 SLQ-200K Sonata suite.

A primary design characteristic of the Sejong the Great-class is its vertical launch system (VLS) capacity, which exceeds that of the contemporary Arleigh Burke and Atago-class destroyers. The class utilizes a mix of the Mk 41 VLS and the Korean Vertical Launching System (K-VLS). Batch II ships further incorporate the K-VLS II to accommodate long-range air defense missiles and ballistic missiles. The vessels are designed with a hangar and helipad to operate two Super Lynx or SH-60 Seahawk helicopters.

The Republic of Korea Navy announced the name of the lead ship, ROKS Sejong the Great (DDG-991), in April 2007. The vessel entered service in December 2008. The class demonstrated its tracking capabilities in April 2009 during the monitoring of a North Korean missile launch. Two additional Batch I ships, ROKS Yulgok Yi I and ROKS Seoae Ryu Seong-ryong, were commissioned by August 2012. The Batch II program began with a construction contract in October 2019. The first Batch II vessel, ROKS Jeongjo the Great (DDG-995), was commissioned in November 2024. A second Batch II ship, ROKS Dasan Jeong Yak-yong, was launched in September 2025, with a third hull remaining under construction.