According to the 2025 Population and Housing Census released by the Ministry of Data and Statistics, people aged 65 and older accounted for 20.7 percent of the population, or 10.72 million.
Children aged 14 and younger made up just 10.1 percent, leaving the elderly population more than twice as large.
The shift accelerated over the past year. The number of seniors increased by 601,000, or 5.9 percent, while the youth population fell by 196,000, or 3.6 percent.
The working-age population, defined as those aged 15 to 64, fell by 393,000 to 35.87 million, with its share of the total population slipping to 69.2 percent — the first time it has fallen below the 70 percent mark since comparable records began in 2015. The decline has continued since 2018.
The old-age dependency ratio — the number of people aged 65 and older per 100 working-age residents — climbed to 29.9 from 27.9 a year earlier, meaning roughly three working-age people now support one senior.
The aging index — the number of seniors for every 100 children under 15 — also climbed to 205.2 from 186.7 a year earlier.
The country's median age rose to 46.8 years, up 0.6 years from the previous year. People in their 50s accounted for the largest share of the population at 16.7 percent, followed by those in their 60s at 15.3 percent and 40s at 14.8 percent.
Among 43.23 million Korean adults aged 18 and older, 29.6 percent were single, while 56.3 percent were married and 14.1 percent were divorced or widowed.
Marriage was increasingly delayed among younger adults. More than half of Koreans in their 30s were unmarried, with the share reaching 54.7 percent. The figure dropped to 21.9 percent among those in their 40s, while 96.0 percent of people in their 20s or younger were unmarried.
The trend was also reflected in household composition. One- and two-person households accounted for 66.1 percent of all ordinary households, while the average household size fell to 2.16 people.
Regionally, Seoul recorded the country's highest unmarried rate at 37.1 percent and the lowest marriage rate at 51.1 percent. South Jeolla Province posted the lowest unmarried rate at 22.2 percent, while Sejong recorded the highest marriage rate at 64.4 percent.
Despite the sweeping demographic changes, the country's total population was little changed. As of Nov. 1, 2025, the population stood at 51.82 million, up just 12,000 people, or 0.02 percent, from a year earlier.
Behind the broadly stable population, Korean nationals continued to decline while the foreign population expanded. The number of Korean nationals fell by 50,000, marking a fifth consecutive annual decline driven largely by persistently low birth rates. Meanwhile, the foreign population rose by 70,000, or 3.2 percent, to 2.11 million, largely reflecting increases in international students, trainees and seasonal workers.
Foreign residents also remained substantially younger than the domestic population. Nearly 90 percent of foreigners were of working age, compared with 68.4 percent of Korean nationals, highlighting their growing role in offsetting labor-force shortages as the country's population continues to age.
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