Yi Seung-Hun (1756 – April 8, 1801, Ja: Jasul (子述), Ho: Mancheon, baptismal name Peter) was one of the first Catholic martyrs in Korea. In 1801, the Korean Catholic Church was subject to the first major repression by the government (the Sinyu Persecution) in which more than 300 people were killed. Yi was martyred by beheading on the 26th of the 2nd lunar month (April 8), 1801. This incident has come to be known as the Catholic Persecution of 1801. Little written material remains from this period but a collection of texts by several of the first believers, known as Mancheon yugo, was discovered in about 1970. Mancheon was the ho of Yi Seung-hun, whose writings occupy a major part of the book, together with texts written by Yi Byeok etc. It is not known when or by whom the collection was made, and although it is sometimes claimed to be in the handwriting of Jeong Yak-yong, this does not seem to be the case.
Yi Seung-hun, a member of the Korean elite, encountered Catholicism in the late 18th century. Baptized in Beijing in 1784, he introduced the faith to others, including influential figures like Gwon Cheol-sin and the Jeong brothers. After the death of Yi Byeok, a pivotal figure in the group, Yi Seung-hun assumed a leading role. By 1786, they were worshiping in Seoul, facing scrutiny from authorities. Despite challenges, the community grew, practicing under temporary clerics until an ordained priest arrived in 1795. Yi Seung-hun and Jeong Yak-jong emerged as prominent leaders, and Yi Seung-hun's wife was related to Jeong Yak-jong.

What was Yi Seung-Hun's family background and how did his father initially respond to Catholic teachings?
Yi Seung-Hun hailed from the Pyeongchang clan, and his father, initially interested but later opposed Catholic teachings.

How did Yi Seung-Hun come to be associated with Catholicism and what significant event occurred during his visit to Beijing in 1784?
Introduced to Catholicism by Yi Byeok in 1779, Yi Seung-Hun was baptized in Beijing in 1784, becoming the first Korean yangban class member to be formally baptized as a Christian.

Who were some key individuals influenced by Yi Seung-Hun's evangelization efforts?
Gwon Cheol-sin, Gwon Il-sin, and the Jeong brothers Yak-jong, Yak-jeon, and Yak-Yong were influenced by Yi Seung-Hun's evangelization.

What actions did Yi Byeok take regarding the Catholic faith, and how did this impact Yi Seung-Hun's role?Yi Byeok studied Catholic books before embracing the faith and encouraged Yi Seung-Hun to baptize others; after his death in 1786, Yi Seung-Hun assumed a leadership role.

How did the Catholic community in Seoul evolve following Yi Byeok's passing in 1786?
After Yi Byeok's passing, Yi Seung-Hun and Jeong Yak-jong became key leaders in Seoul's Catholic community.

When did formal ordination of priests begin in Korea's Catholic community, and how did it affect the community's growth?
Ordination of priests began in 1795 with the arrival of the Chinese priest Zhu Wenmiao, leading to significant growth in the Church, which had grown to over 4000 members by then.

How did Yi Seung-Hun's life end, and what significant event marked the major government suppression of the Korean Catholic Church in 1801?
Yi Seung-Hun was martyred by beheading in the Sinyu Persecution of 1801, marking a government-led suppression where over 300 people were killed, signifying a major event in the history of the Korean Catholic Church.

Yi Seung-hun - Wikipedia