Sejo of Joseon, born Grand Prince Suyang, became the seventh king of Joseon following a tumultuous series of events after the death of King Sejong in 1450. His rise to power involved strategic political maneuvering and the use of force. After Sejong's death, the throne passed to Suyang's ill brother, King Munjong, who died in 1452. Munjong's young son, Yi Hong-wi (later King Danjong), succeeded him but was too young to govern effectively. The government was initially controlled by Chief State Councillor Hwangbo In and Left State Councillor General Kim Jong-seo, with Princess Gyeonghye acting as Danjong's guardian. Suyang, seeing an opportunity, staged a coup in 1453, killing Kim Jong-seo and his faction. This move allowed him to seize control of the government. He later arrested and executed his brother, Grand Prince Anpyeong, consolidating his power further.

In 1455, Suyang forced King Danjong to abdicate and declared himself the ruler, taking the name Sejo. His reign witnessed additional power struggles, including a plot by his younger brother, Grand Prince Geumsung, and several scholars to restore Danjong to the throne. Sejo responded by demoting Danjong from King Emeritus to Prince Nosan and later ordering his nephew's death.

Despite the violence associated with his ascent to power, Sejo was an effective ruler. He continued the centralization of royal power started by King Taejong, weakening the State Council and exerting greater control over government officials. He developed administrative systems for more accurate population counts and troop mobilization. His foreign policy was aggressive, notably against the Jurchens in the north.

Sejo also contributed to the cultural and intellectual life of Joseon. He encouraged the publication of works on history, economy, agriculture, and religion. He compiled several books, including Seokbosangjeol, a biography of Gautama Buddha. Sejo also championed Korean music in royal rituals, modifying compositions by his father, King Sejong. One of his significant contributions was compiling the Grand Code for State Administration, a foundational document for Korean constitutional law. Sejo died in 1468, and his second son, Yejong of Joseon, succeeded him. He was buried at Gwangneung in Namyangju, Gyeonggi Province, South Korea.