Sejo, personal name Yi Yu, sometimes known as Grand Prince Suyang, was the seventh monarch of the Joseon dynasty of Korea. He was the second son of Sejong the Great and the uncle of King Danjong, against whom he led a coup d'état in 1453.

Yi Si-ae's Rebellion was an armed rebellion in 1467 in Hamgil Province led by General Yi Si-ae, a member of Yangban landowners in Kilju, Hamgil Province, to rebel against the centralized policy of King Sejo.