Korean language is an East Asian language spoken by about 80 million people. It is a member of the Koreanic language family and is the official and national language of both Koreas: the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea), with different standardized official forms used in each territory. It is also one of the two official languages in the Yanbian Korean Autonomous Prefecture and Changbai Korean Autonomous County of the People's Republic of China. Historical and modern linguists classify Korean as a language isolate; however, it does have a few extinct relatives, which together with Korean itself and the Jeju language (spoken in the Jeju Province and considered somewhat distinct) form the Koreanic language family. This implies that Korean is not an isolate, but a member of a small family. The idea that Korean belongs to the controversial Altaic language family is discredited in academic research. Korean is now often included in the Paleosiberian family, a group of ancient languages in Northeast Asia. The Korean language is agglutinative in its morphology and SOV in its syntax.

Korean has numerous small local dialects (called mal (말) [literally "speech"], saturi (사투리), or bang'eon (방언 in Korean). The standard language (pyojun-eo or pyojun-mal) of both South Korea and North Korea is based on the dialect of the area around Seoul (which, as Hanyang, was the capital of Joseon-era Korea for 500 years), though the northern standard after the Korean War has been influenced by the dialect of P'yŏngyang. All dialects of Korean are similar to each other and largely mutually intelligible (with the exception of dialect-specific phrases or non-Standard vocabulary unique to dialects), though the dialect of Jeju Island is divergent enough to be sometimes classified as a separate language. One of the more salient differences between dialects is the use of tone: speakers of the Seoul dialect make use of vowel length, whereas speakers of the Gyeongsang dialect maintain the pitch accent of Middle Korean. Some dialects are conservative, maintaining Middle Korean sounds (such as z, β, ə) which have been lost from the standard language, whereas others are highly innovative.

Korean is spoken by the Korean people in North Korea and South Korea and by the Korean diaspora in many countries including the People's Republic of China, the United States, Japan, and Russia. Currently, Korean is the fourth most popular foreign language in China, following English, Japanese, and Russian. Korean-speaking minorities exist in these states, but because of cultural assimilation into host countries, not all ethnic Koreans may speak it with native fluency.