Catholic martyr who headed the Myeongdohoe and wrote the Jugyo Yoji; baptismal name Augustine; beatified in 2014

| Life | 1760 ~ 1801 |
| Era | 조선 후기 |
| Clan | 나주 정씨 |
Jeong Yak-jong (丁若鍾, 1760-1801) was a scholar of Jeongjo's reign and a Catholic martyr. From Naju, with the baptismal name Augustine, he was the third son of Jinju Magistrate Jeong Jae-won, born in Gwangju (now Neungnae-ri, Joan-myeon, Namyangju). His older brothers were Jeong Yak-hyeon and Jeong Yak-jeon, and his younger brother Jeong Yak-yong. In youth he studied the learning of Yi Ik and for a time Daoism.
The Naju Jeong clan association summarises that he learned doctrine from his brother Yak-jeon and was baptised by Yi Seung-hun in 1786, choosing the name Augustine because his own long search resembled that saint's. After the 1787 Banhoe incident, when the family turned against Catholicism, he moved his wife and children across the Han River to Bunwon in Yanggeun and taught doctrine to lower-class people in his home. Living and practising faith with people across status lines is seen as distinctive.
In 1795 he joined Yi Seung-hun in receiving the Chinese priest Zhou Wenmo, and in early 1799, when Zhou founded the lay Myeongdohoe, he became its first president. His Jugyo Yoji in two volumes, written entirely in Hangul so that believers and women who could not read Chinese could follow, is the first such catechism; Zhou reportedly said it was more needed than firewood. He was writing the Seonggyo Jeonseo when persecution struck.
When the 1801 Sinyu persecution began, a chest holding holy images, books and letters was discovered as it was moved; he was arrested on the 11th day of the 2nd lunar month and interrogated many times without yielding. He was beheaded outside Seosomun Gate on the 26th of the 2nd lunar month in 1801. The clan association says that on the way to the execution ground he urged the crowd to worship the Lord of Heaven and said it was better to die looking at the sky. His son Jeong Cheol-sang was also beheaded, and Jeong Yak-jong was beatified on 16 August 2014 during Pope Francis's visit to Korea.
Baptised in 1786, he found the family turning from Catholicism after the 1787 Banhoe incident and the 1791 Jinsan incident; in conflict over ancestral rites he left Majae for Bunwon in Yanggeun. His brothers Yak-jeon and Yak-yong distanced themselves from the faith around this time.
As first president of the Myeongdohoe founded by Father Zhou, he led the lay organisation. The clan association describes the Jugyo Yoji as a two-part catechism of 43 chapters covering proofs of God, criticism of Buddhism, Daoism and folk belief, and creation and redemption.
The clan association explains that when persecution began, a servant was caught moving the chest to the house of Hwang Sa-yeong, and the books, sacred items and letters inside became evidence for the attack on the Southerners. Under the regency of Queen Jeongsun, Yi Ga-hwan, Gwon Cheol-sin and others also suffered greatly.
Wikipedia reports that Jeong Yak-jong was beatified on 16 August 2014 at the ceremony in Gwanghwamun Square, Seoul. His son Jeong Cheol-sang was also beheaded and martyred in the Sinyu persecution. His son Jeong Ha-sang had already been canonised in 1984.
He was executed outside Seosomun Gate, an area now the Seosomun martyrs' shrine. The location of his grave was not confirmed here.
His children were Jeong Cheol-sang (Charles, 1782-1801), Jeong Ha-sang (Paul, 1795-1839) and Jeong Jeong-hye (Elizabeth, 1797-1839); with his wife Yu Jo-i (Cecilia) all were martyred. Jeong Ha-sang was canonised in 1984.