This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Yi Seung-hun, a Korean scholar travelling with a diplomatic mission to Beijing, was baptised there in 1784 and returned home carrying religious books and a crucifix. He and a small circle of fellow scholars began instructing and baptising one another, and by early 1785 a self-organised lay Catholic community was meeting and worshipping in a private house in Seoul, years before any ordained priest, Western or otherwise, had ever set foot in Korea to plant it.
The Choson dynasty's government answered the new faith with repeated waves of persecution rather than tolerance. Yi Seung-hun himself was executed in 1801, one of several hundred converts killed in that year's purge alone, and further rounds of persecution followed across the decades afterward, long before Catholicism gained any legal standing in Korea.
What this changed for Christianity's spread was the arrival of a pattern almost nowhere else repeated, a national church that Koreans themselves founded, organised and led before any missionary ever reached them, rather than one planted from outside by a sent mission. That lay foundation gave Korean Catholicism a homegrown identity from its very first year, one persecution could not erase even as the community's own founder was among the earliest believers it killed.