The Korean people originally may have had links with the people of Central Asia, the Lake Baikal region, Mongolia, and the coastal areas of the Yellow Sea. Tools of Paleolithic type and other artifacts found in Sokch'ang, near Kongju, are quite similar to those of the Lake Baikal and Mongolian areas. The population of South Korea is highly homogeneous, although the number of foreigners is growing, especially in the major urban areas. In addition to American soldiers, urban Chinese, and foreign nationals in business or the diplomatic corps, tens of thousands of workers have come to South Korea from China and Southeast Asia.

All Koreans speak the Korean language, which is often classified as one of the Altaic languages, has affinities to Japanese, and contains many Chinese loanwords. The Korean script, known in South Korea as Hangul (Han'gul) and in North Korea as Choson muntcha, is composed of phonetic symbols for the 10 vowels and 14 consonants. Korean often is written as a combination of Chinese ideograms and Hangul in South Korea, although the trend there is toward using less Chinese. A number of English words and phrases have crept into the language as a result of the American presence in the country since 1950.