Sejong (Korean: 세종; Hanja: 世宗; May 15, 1397 – April 8, 1450), commonly known as Sejong the Great (세종대왕; 世宗大王), was the fourth monarch of the Koreanic state Joseon. He ruled from 1418 to his death in 1450. He is widely regarded as the greatest king in Korean history, and is remembered for the creation of Hangul, the native alphabet of the Korean language.
Sejong was born the third son of the future King Taejong (r. 1400–1418). He was regarded as gifted, moreso than the troubled crown prince Grand Prince Yangnyŏng. In mid-1418, Yangnyŏng was deposed and Sejong made the crown prince. Months later, Taejong abdicated and Sejong was crowned king. Taejong served as king emeritus until his death in 1422.