Over the past few decades, Christianity has increased dramatically in South Korea. About 18 percent of the population professed to be Protestants and around 10 percent Roman Catholics in the year 2005 blank">http://www.newsnjoy.co.kr/news/articleView.html?idxno=17072 . The capital of South Korea, Seoul contains eleven of the world's twelve largest Christian congregations. South Korea is also the world's second largest missionary (with the United States as the first) nation. Sending South Korean missionaries are particularly prevalent in _10/40 Window nations that are hostile to Westerners. In 2000 there were 10,646 Korean Protestant missionaries in 156 countries, along with a large but undisclosed number of Catholic missionaries. The impact of Christianity on the Korean culture has been considerable, and is partly responsible for a steady decline in the membership and influence of Buddhism, Shamanism and Confucianism, which have traditionally had deep roots in Korean culture. A number of Korean Christians, including David Yonggi Cho (조용기), senior pastor of the colossal Yoido Full Gospel Church have attained worldwide prominence. The 1984 visit by Pope John Paul II marked the first canonization ceremony to be held outside of Rome and the largest number of saints ever to be canonized at one time.

Unless otherwise stated, all references in this article to "Korea," "Korean people," and "Korean church" after 1945 apply to South Korea only. Prior to the Korean War of 1950–1953, two thirds of the country's Christians lived in the North, but most subsequently fled to the South. It is not known how many Christians remain in the North.

Very few countries have witnessed a dramatic rise in Christianity as it occurred in Korea within a few decades of the twentieth century. According to the CIA factbook, the Christians and Buddhists are each 26% of the population https://www.cia.gov/library/publications/the-world-factbook/geos/ks.html. Other sources claim the Christians are about 49% http://go.hrw.com/atlas/norm_htm/skorea.htm. The discrepancy arises because a large proportion of the population does not officially adhere to an organized religion. In any case, Christianity has overtaken Buddhism in Korea in four decades during 1960s-1980s "Conversion Boom" period http://www.tparents.org/Library/Religion/Cta/Korean-Christianity.htm. In 1960s, the Korean Protestants bared reached one million mark. In the next three decades, the number of Protestants increased faster than in any other country http://www.kf.or.kr/KoreaFocus/essays.asp?vol=29&no=817§ion=4.