According to the report by Statistics Korea, the number of people aged 65 and older stood at 8.53 million this year.
The South Korean population is projected to peak in 2028 before going on a downward curve, the report showed.
However, the graying of South Korea will accelerate, with the number of elderly people rising to 12.98 million in 2030 and 17.22 million in 2040.
By 2050, the number of elderly people could account for 43.9 percent of the country's population, according to the report.
The fast-aging population, coupled with record low birthrates, could become a burden on the nation's finances as the cost of health and welfare services for senior citizens increase.
In 2020, the number of elderly heads of households stood at 4.73 million, and 35.1 percent of them were one-person households, the data showed.
Meanwhile, divorces among people aged 65 and older have been growing fast.
The report showed that the number of divorces filed by men in the age group came to 9,854 last year, and the corresponding number for females was 5,285.
The figures accounted for 11.1 percent and 13.7 percent, respectively, of the country's divorces last year. (Yonhap)