The two most pervasive religions in Korea are Buddhism and Christianity. Buddhism has a long history in Korea and has traditionally been the accepted religion among most Koreans, though with modernization and the influx of Christianity, this has certainly changed.
Along with Taoism, Buddhism entered the Korean cultural landscape in the 4th century, coming from China. Buddhism remains popular among the more traditional eastern part of the country and in conservative cities like Daegu and Andong.
It’s important to remember that even though a Korean might not belong to a certain religion, inherent cultural elements might be construed as shamanism, such as the worshipping of ancestors during Chuseok festivals or other times of the year.
Cults and sect are prevalent in Korea, the most famous probably being the Unification church or Sun Meyong Moon, with their mass wedding rituals.