Cheonan, city, South Chungcheong do (province), western South Korea, south of Seoul. A transportation junction since ancient times, it is known by a famous folk song, “Cheonan Samgeori” (samgeori meaning “three-way intersection”). The city is connected with the surrounding provinces by rail and road, and the Seoul subway system provides a further link between the two cities. Cheonan is the market center for agricultural products (rice, barley, and vegetables) from the northern part of South Chungcheong province. The picturesque old Seongbul Temple (Seongbul-sa) is on the nearby mountain. The area around Onyang, a few miles to the west, has some of the country’s largest hot-spring spas and is the site of Hyeonchung Temple (Hyeonchung-sa). Pop. (2020) 682,199.