Many people come from around the globe to live in South Korea to work or study. The number of resident foreigners has increased rapidly since the 1990s with the influx of foreign workers, foreign nationals, international students, and marriage immigrants. The total number of foreigners reached a record high of 2.52 million in 2019. In 2020, due to the impact of COVID-19, the number of foreigners dropped by nearly half a million to 2.04 million. Most foreign residents are from other Asian countries, especially China, Vietnam, and Thailand. Nearly one million are Chinese: 250,000 Chinese and 650,000 Korean Chinese (Chinese of Korean ethnicity). 

 

 The proportion of foreigners aged 25–34 is high. However, the age and gender demographics of foreigners residing in Korea vary greatly by country. For example, among Chinese nationals, there are more Korean Chinese women than men, but more non-Korean Chinese men than women. Also, most Korean Chinese are over the age of 50, while most non-Chinese are under the age of 50. African, Central Asian, and Southeast Asian countries, in general, have a high proportion of men, with the exception of a few countries, such as Thailand. The United States also shows a similar pattern. A higher sex ratio of the Indonesian population in Korea is due to religious reasons. On the other hand, the proportion of female Japanese in Korea is overwhelmingly high. 

 

 In 2020, 390,000 immigrants stayed in Korea beyond the expiration date of their visas. As the COVID-19 pandemic made it difficult for foreign workers to return to their home countries, the rate of illegal immigration in Korea rose to 19.3%, the highest since 2008. 

 

 By 2019, the Seoul Metropolitan Area had 1.32 million foreign residents, accounting for more than half of all foreigners living in Korea. The proportion of foreign residents in the total population is relatively high in the -si/-gun/-gu areas in the Seoul Metropolitan Area and in its neighboring regions. The proportion of foreign residents is continuously increasing across the nation as the employment of foreign workers expands in the manufacturing sector and in non-manufacturing sectors such as construction, wholesale and retail, and agriculture.