Demographic features of South Korea's population include population density, ethnicity, education level, health, economic status, religious affiliations, and other aspects of the population. The common language and especially culture are widely considered more important elements by South Koreans in terms of identity than citizenship.

In 2012, South Korea's population surpassed 50 million citizens for the first time in history, and by the end of 2021, the country's population had peaked at approximately 51.77 million people. However, in recent years the total fertility rate (TFR) of South Korea has stayed below the replacement requirement of 2.1, leading some researchers to suggest that if current trends continue, the country's population will shrink to approximately 28 million people by the end of the 21st century.World Population Prospects 2019 by the United Nations, DESA, Population Division. In 2018, fertility in South Korea became a topic of international debate after only 26,500 babies were born in October and an estimated 325,000 babies for the year, causing the country to achieve the lowest birth rate in the world. In a further indication of South Korea's dramatic decline in fertility, in 2020 the country recorded more deaths than births, resulting in a population decline for the first time since modern records began. In 2026, South Korea had the lowest birthrate in the world.

South Korea's population decline has been a direct result of record-low birth rates, which have been, according to many experts and researchers, a consequence of the country's high economic inequality, relatively high costs of living, low wages for an OECD member country, lack of job opportunities for young adults, and rising housing costs. Additionally, South Korea is also the country with the highest suicide rate among OECD member states and the wider developed world.

In South Korea, a variety of different Asian people had migrated to the Korean Peninsula in past centuries; however, few have remained permanently. South Korea is a highly homogenous nation, but has in recent decades become home to a number of foreign residents (5.44%), whereas North Korea has not experienced this trend. However, many of them are ethnic Koreans with foreign citizenship. Many residents from China, post-Soviet states, the United States, and Japan are, in fact, repatriated ethnic Koreans (labeled "Overseas Koreans") who may meet criteria for expedited acquisition of South Korean citizenship. For example, migrants from the People's Republic of China (PRC) make up 35.23% of foreign nationals; however, approximately 70% of the Chinese citizens in Korea are (), PRC citizens of Korean ethnicity. (Note: According to the article, approximately 443,566 people are considered to be Chinese residents in South Korea with Korean ethnicity.)

Population trends

The population of South Korea showed robust growth since the republic's establishment in 1948, and then dramatically slowed down with the effects of its economic growth. In the first official census, taken in 1949, the total population of South Korea was calculated at 20,188,641 people. The 1985 census total was 40,466,577. Population growth was slow, averaging about 1.1% annually during the period from 1949 to 1955, when the population registered at 21.5 million. Growth accelerated between 1955 and 1966 to 29.2 million or an annual average of 2.8%, but declined significantly during the period 1966 to 1985 to an annual average of 1.7%. Thereafter, the annual average growth rate was estimated to be less than 1%, similar to the low growth rates of most industrialized countries and to the target figure set by the Ministry of Health and Social Affairs for the 1990s. As of January 1, 1989, the population of South Korea was estimated to be approximately 42,200,000.

The proportion of the total population under fifteen years of age has risen and fallen with the growth rate. In 1955, approximately 41.2% of the population was under fifteen years of age, a percentage that rose to 43.5% in 1966 before falling to 38.3% in 1975, 34.2% in 1980, and 29.9% in 1985. In the past, the large proportion of children relative to the total population put great strains on the country's economy, particularly because substantial resources were invested in education facilities. With the slowdown in the population growth rate and a rise in the median age (from 18.7 years to 21.8 years between 1960 and 1980), the age structure of the population has begun to resemble the columnar pattern typical of developed countries, rather than the pyramidal pattern found in most parts of the Third World.

The decline in the population growth rate and in the proportion of people under fifteen years of age after 1966 reflected the success of official and unofficial birth control programs. The government of President Syngman Rhee (1948–60) was conservative in such matters. Although Christian churches initiated a family planning campaign in 1957, it was not until 1962 that the government of Park Chung Hee, alarmed at the way in which the rapidly increasing population was undermining economic growth, began a nationwide family planning program. Other factors that contributed to a slowdown in population growth included urbanization, later marriage ages for both men and women, higher education levels, a greater number of women in the labor force, and better health standards.

Public and private agencies involved in family planning included the Ministry of Health and Social Affairs, the Ministry of Home Affairs, the Planned Parenthood Federation of Korea, and the Korea Institute of Family Planning. In the late 1980s, their activities included the distribution of free birth control devices and information, classes for women on family planning methods, and the granting of special subsidies and privileges (such as low-interest housing loans) to parents who agreed to undergo sterilization. There were 502,000 South Koreans sterilized in 1984, as compared with 426,000 in the previous year.

The 1973 Maternal and Child Health Law legalized abortion. In 1983, the government began suspending medical insurance benefits for maternal care for pregnant women with three or more children. It also denied tax deductions for education expenses to parents with two or more children.

As in China, cultural attitudes posed problems for family planning programs. A strong preference for sons—who in Korea's traditional Confucian value system are expected to care for their parents in old age and carry on the family name—means that parents with only daughters usually continued to have children until a son is born. The government encouraged married couples to have only one child. This has been a prominent theme in public service advertising, which stresses "have a single child and raise it well."

Total fertility rates (the average number of births a woman will have during her lifetime) fell from 6.1 births per female in 1960 to 4.2 in 1970, 2.8 in 1980, and 2.4 in 1984. The number of live births, recorded as 711,810 in 1978, grew to a high of 917,860 in 1982. This development stirred apprehensions among family planning experts of a new "baby boom." By 1986, however, the number of live births had declined to 806,041.

Decline in population growth continued, and between 2005 and 2010 total fertility rate for South Korean women was 1.21, one of the world's lowest according to the United Nations. Fertility rate well below the replacement level of 2.1 births per female has triggered a national alarm, with some predicting an aging society unable to grow or support its elderly. Recent Korean governments have prioritized the issue on their agenda, promising to enact social reforms that will encourage women to have children.

The country's population increased to 46 million by the end of the twentieth century, with growth rates ranging between 0.9% and 1.2%. An early 1992 estimate had projected that the population would stabilize around 2023 at about 52.6 million people. Subsequent projections released by Statistics Korea in December 2023 found that the total population reached 51.67 million in 2022 and, after a brief peak of roughly 51.75 million in 2024, is expected to decline rather than stabilize, falling to 50.06 million by 2040 and to 36.22 million by 2072. In the words of Asiaweek magazine, the "stabilized tally will approximate the number of Filipinos in 1983, but squeezed into less than a third of their [the Philippines'] space."

As of early 2019, the birth rate of South Korea reached an alarmingly low number. In February 2019, the Korean TFR fell to 0.98, well below the replacement level of 2.1 births. South Korea is now the fastest-aging developed country in the world. The Korean government (and its failing actions against the birth rate issue) and the worsening economic environment for young people are blamed as the main causes.

Population settlement patterns

South Korea is one of the world's most densely populated countries, with an estimated 425 people per square kilometer in 1989—over sixteen times the average population density of the United States in the late 1980s. By comparison, China had an estimated 114 people, the Federal Republic of Germany (West Germany) 246 people, and Japan 323 people per square kilometer in the late 1980s. Because about 70% of South Korea's land area is mountainous and the population is concentrated in the lowland areas, actual population densities were in general greater than the average. As early as 1975, it was estimated that the density of South Korea's thirty-five cities, each of which had a population of 50,000 or more inhabitants, was 3,700 people per square kilometer. Because of continued migration to urban areas, the figure was higher in the late 1980s.

In 1988 Seoul had a population density of 17,030 people per square kilometer as compared with 13,816 people per square kilometer in 1980. The second largest city, Busan, had a density of 8,504 people per square kilometer in 1988 as compared with 7,272 people in 1980. Gyeonggi Province, which surrounds the capital and contains Incheon, the country's fourth largest city, was the most densely populated province; Gangwon Province in the northeast was the least densely populated province.

According to the government's Economic Planning Board, the population density will be 530 people per square kilometer by 2023, the year the population is expected to stabilize.

Rural areas in South Korea consist of agglomerated villages in river valleys and range from a few houses to several hundred. These villages are located in the south that are backed by hills and give strong protection from winter winds.

Since 1960, the pace of urbanization in South Korea has hit a considerable decline in population of rural areas and the traditional rural lifestyle has been slowly fading away.

Fertility

Over the past 20 years, South Korea has recorded some of the lowest fertility and marriage levels in the world. As of 2024, it is the country with the world's lowest total fertility rate (TFR), standing at 0.75. Additionally, the country's capital, Seoul, registered a TFR of 0.64, which was likely the lowest level anywhere in the world. entering pediatrics out of the fear that the field has no future. Due to how medical insurance is structured in South Korea, pediatric care relies especially on volume to compensate for its low reimbursement rates. The number of pediatric facilities in Seoul fell by 12.5 percent between 2018 and 2022, compared to an increase of 76.8 percent for psychiatry clinics and a 41.2 percent rise for anesthesiology centers. Conditions such as overcrowded waiting rooms and a shortage of hospital beds have led to the death of at least one child. The difficulty in obtaining pediatric care is causing many South Korean couples to reconsider having babies.

Age structure

Population of South Korea by age and sex (demographic pyramid)