Korean is the native language for about 81 million people, mostly of Korean descent. It is the national language of both North Korea and South Korea. In the south, the language is known as Hangugeo (South Korean: 한국어) and in the north, it is known as Chosŏnŏ (North Korean: 조선어). Since the turn of the 21st century, aspects of Korean popular culture have spread around the world through globalization and cultural exports.

Beyond Korea, the language is recognized as a minority language in parts of China, namely Jilin, and specifically Yanbian Prefecture, and Changbai County. It is also spoken by Sakhalin Koreans in parts of Sakhalin, the Russian island just north of Japan, and by the Koryo-saram in parts of Central Asia. The language has a few extinct relatives which—along with the Jeju language (Jejuan) of Jeju Island and Korean itself—form the compact Koreanic language family. Even so, Jejuan and Korean are not mutually intelligible. The linguistic homeland of Korean is suggested to be somewhere in contemporary Manchuria. The hierarchy of the society from which the language originates deeply influences the language, leading to a system of speech levels and honorifics indicative of the formality of any given situation.

Modern Korean is written in the Korean script (한글; Hangeul in South Korea, 조선글; Chosŏn'gŭl in North Korea), an alphabet system developed during the 15th century for that purpose, although it did not become the primary script until the mid 20th century (Hanja and mixed script were the primary script until then). The script uses 24 basic letters (jamo) and 27 complex letters formed from the basic ones.

Interest in Korean language acquisition (as a foreign language) has been generated by longstanding alliances, military involvement, and diplomacy, such as between South Korea–United States and China–North Korea since the end of World War II and the Korean War. Along with other languages such as Chinese and Arabic, Korean is ranked at the top difficulty level for English speakers by the United States Department of Defense.

Modern Korean descends from Middle Korean, which in turn descends from Old Korean, which descends from the Proto-Koreanic language, which is generally suggested to have its linguistic homeland somewhere in Manchuria. Whitman (2012) suggests that the proto-Koreans, already present in northern Korea, expanded into the southern part of the Korean Peninsula at around 300 BC and coexisted with the descendants of the Japonic Mumun cultivators (or assimilated them). Both had influence on each other and a later founder effect diminished the internal variety of both language families.

Since the establishment of two independent governments, North–South differences have developed in standard Korean, including variations in pronunciation and vocabulary chosen. While there tends to be strong political conflict between North and South Korea regarding these linguistic "differences," regional dialects within each country actually display greater linguistic variations than those found between North and South Korean standards. Nevertheless, these dialects remain largely mutually intelligible.

The Chinese language, written with Chinese characters and read with Sino-Xenic pronunciations, was first introduced to Korea in the 1st century BC, and remained the medium of formal writing and government until the late 19th century. Korean scholars adapted Chinese characters (known in Korean as Hanja) to write their own language, creating scripts known as idu, hyangchal, gugyeol, and gakpil. These systems were cumbersome, due to the fundamental disparities between the Korean and Chinese languages, and accessible only to those educated in classical Chinese. Most of the population was illiterate.^{[citation needed]}

In the 15th century King Sejong the Great personally developed an alphabetic featural writing system, known today as Hangul, to promote literacy among the common people. Introduced in the document Hunminjeongeum, it was called eonmun ('colloquial script') and quickly spread nationwide to increase literacy in Korea.