Sejong the Great (May 15, 1397 – April 8, 1450, r. 1418–1450) was the fourth king of the Joseon Dynasty of Korea. During his reign, he reinforced Korean Confucian policies and executed major legal amendments (공법; 貢法). He also used the creation of Hangul and the advancement of technology to expand his territory. He was the third son of King Taejong and Queen Consort Wonkyeong.

Sejong is one of only two Korean rulers posthumously honored with the appellation "the Great", the other being Gwanggaeto the Great of Goguryeo.

Sejong was born on May 15, 1397, the third son of King Taejong. When he was twelve, he became Grand Prince Chungnyeong. As a young prince, Sejong excelled in various studies and was favored by King Taejong over his two older brothers.

Sejong's ascension to the throne was different from those of most other kings. Taejong's eldest son, Yangnyeong (양녕대군), viewing himself as lacking in the requisite skills for kingship, believed that his younger brother Sejong was destined to become king. He believed it was his duty to place Sejong as king, so he behaved rudely in court and was soon banished from Seoul. This plot ultimately brought Sejong to the throne. The eldest prince became a wandering traveler and lived in the mountains. The second son traveled to a Buddhist temple, where he became a monk.