The Korean diaspora consists of around 7.3 million people, both descendants of early emigrants from the Korean Peninsula, as well as more recent emigrants from Korea. Around 84.5% of overseas Koreans live in just five countries: the United States, China, Japan, Canada, and Uzbekistan. Other countries with greater than 0.5% Korean minorities include Brazil, Russia, Kazakhstan, Vietnam, the Philippines, and Indonesia. All of these figures include both permanent and temporary migrants. Outside of Continental and East Asia, there are sizeable Korean communities have formed in Germany, the United Kingdom, France, the United States, Canada, Australia, and New Zealand.

There are currently a number of official and unofficial appellations used by the authorities of the two Korean states, as well as a number of Korean institutions for Korean nationals, expatriates, and descendants living abroad. Thus, there is no single name for the Korean diaspora.

The historically used term gyopo (교포/僑胞, also spelled kyopo, meaning "nationals") has come to have negative connotations as referring to people who, as a result of living as sojourners outside the "home country", have lost touch with their Korean roots. As a result, others prefer to use the term dongpo (동포/同胞, meaning "brethren" or "people of the same ancestry"). Dongpo has a more transnational implication, emphasising links among various overseas Korean groups, while gyopo has more of a purely national connotation referring to the Korean state. Another recently popularized term is gyomin (교민/僑民, meaning "immigrants"), although it is usually reserved for Korean-born citizens that have moved abroad in search of work, and as such is rarely used as a term to refer to the entire diaspora.

In North Korea, Korean nationals living outside Korea are called haeoe gungmin (해외국민), whereas South Korea uses the term jaeoe gungmin (재외국민) to refer to the entire Korean diaspora. Both terms translate to "overseas national(s)".

Before the modern era, Korea had been a territorially stable polity for centuries. Significant migration out of Korea did not begin until the late 19th century.

During the 1592–1598 Imjin War, tens of thousands of enslaved Koreans were taken from Korea to Japan, with the first shipment being taken in October 1592. Some were allowed to return to Korea, but many were made to stay in Japan, with the famous example of Korean samurai Wakita Naokata (Kim Yŏch'ŏl). Some were made saints in the 17th-century (205 Martyrs of Japan). The Portuguese then sent some of them elsewhere, namely Portuguese Macau. A community of several thousand Koreans formed near the Church of Saint Paul. Others were sent to Manila in the Spanish Philippines, at least one to Goa, and likely one (Thome Corea) to Ambon Island, where he died in 1623. An António Corea was taken to Florence and Rome, and is possibly the first Korean to set foot in Europe.

The international trade of Korean slaves declined shortly after the end of the Japanese invasions due to a number of prohibitions from various Japanese, Catholic, and Spanish and Portuguese colonial authorities. Despite the near halt in their export from Japan, their labor continued to be used.

Large-scale emigration from Korea began as early as the mid-1860s, mainly into the Russian Far East and Northeast China; these emigrants became the ancestors of the two million Koreans in China and several hundred thousand Koryo-saram.^{[page needed][page needed]}