This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Protestant Christianity in South Korea stood at roughly two percent of the population in 1945, when Japanese colonial rule ended, and had grown to 18.4 percent, about eight million people, by 1991. No other country saw Protestant growth move that fast over the same stretch of decades: the surge is remembered in South Korea as the Conversion Boom, running from the 1960s through the 1980s.
Presbyterianism led that growth from the very start of Protestant work in the country. Horace Underwood planted the first Presbyterian mission in 1885, and Presbyterianism remained the single largest Protestant tradition in South Korea through every decade of the Conversion Boom that followed.
The tradition did not stay one unified body across that growth. A mid century split divided Korean Presbyterianism into several distinct denominations, each continuing to grow along its own line rather than under one roof. By 2019 the Presbyterian Church of Korea, the largest of those bodies on its own, reported around four million attendees across 286 branches.
What that century of growth changed for Presbyterianism's spread was its position at the center of one of the fastest Protestant expansions anywhere in the world. A single 1885 mission became, within little more than a hundred years, the largest Protestant tradition inside a country where Protestant Christianity itself had grown from a small minority to nearly a fifth of the population.