Seongho Yi Ik (1681–1763) was a KoreanNeo-Confucian scholar, early Silhak philosopher and social critic. He was born to a yangban family of the YeojuYi clan. His one disciple of Yi Seo-woo, was Misu Heo Mok and Baikho Yun-hyu's school disciples. second cousin of Yu Hyeong-won. Like most in his position, he studied for the gwageo in order to gain a position of rank; but failed in his first attempt in 1705. Shortly thereafter, his elder brother Yi Jam was beaten to death as part of the Lady Jang incident, and Yi lost interest in government service.
Yi Ik followed in Yu Hyeong-won line of thought extending in this work Seongho Saseol, which covers subjects as government, economy, and the family, and makes detailed proposals for reordering each aspect of Joseon society. His most famous work was Record of Concern for the Underprivileged which lays down the cardinal principles of reform ideas. As Yi attracted many disciples, Silhak gradually emerged as Joseon dynasty's dominant school of thought.
He was born in Ansan in 1681. In 1967 a monument to him, "Tomb of Yi Ik" was erect there.