According to a recent report by Gallup Korea titled Religion of Koreans 1983–2025, only 24 percent of adults in their 20s said they currently practice a religion last year, meaning more than 75 percent described themselves as nonreligious.
The figure compares with 29 percent among people in their 30s, 37 percent in their 40s, 45 percent in their 50s and 52 percent among those aged 60 and older.
Overall, 40 percent of South Korean adults said they had a religion in 2025, including 18 percent Protestant, 16 percent Buddhist and 6 percent Catholic.
The share of religious adults had climbed from 44 percent in 1983 to a peak of 54 percent in 2004 before entering a long decline. It fell to 37 percent in 2022 during the final stages of the COVID-19 pandemic before rebounding slightly last year.
The generational divide, however, remains stark.
Among respondents in their 20s who said they had no religion, 58 percent cited simple lack of interest as the main reason. Another 20 percent said they lacked the mental or time capacity for religious life, while 9 percent pointed to distrust or disappointment with religion and another 9 percent said they preferred to rely on themselves.
Gallup Korea said the decline in religious affiliation over the past two decades has been driven primarily by younger generations.
“The main cause behind the decline in religious populations over the past 20 years was among young people,” the report said. “Not only has the inflow of new young believers decreased, but existing followers have also left organized religion, weakening overall religious communities and accelerating population aging.”
The trend is reshaping the demographic structure of South Korea’s major religions.
Among adults identifying as Buddhists, 56 percent were aged 60 or older, according to the Gallup survey. The proportion stood at 34 percent among Protestants and 32 percent among Catholics, indicating broad aging across faith groups.
Data released last month by the Catholic Bishops' Conference of Korea showed the number of Catholic believers aged 29 or younger fell 34 percent over the past decade, while believers aged 65 and older surged 80.4 percent between 2015 and 2025.
Senior citizens accounted for 28.9 percent of all Catholics in South Korea last year, exceeding the country’s overall elderly population ratio of 21.2 percent. The report said the Korean Catholic Church had effectively entered a “super-aged society” as early as 2019.
The aging trend is also spreading among clergy.
The proportion of diocesan priests aged 65 or older rose steadily from 11 percent in 2015 to 19.7 percent this year, according to Catholic Church statistics. Over the same period, the number of seminarians fell 41.9 percent while newly ordained diocesan priests declined 42.1 percent, suggesting further strain on future clergy recruitment.
Korea’s largest Buddhist sect, the Jogye Order, is facing similar pressures. The number of new monastic entrants has reportedly fallen to about one-third of levels seen two decades ago, while more than 30 percent of monks are now elderly.
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