Busan or Pusan (bōō´sän), Jap. Fusan, city (1995 pop. 3,813,814), extreme SE South Korea, on the Korea Strait. It is the nation's second largest city and largest port, handling most of South Korea's foreign trade. Since 1963, Busan has been a independent metropolitan city with the status of a province. Lying at the head of the Nakdong River basin, it has served as a main southern gateway to Korea from Japan, which, during its rule over Korea (1905–45), developed Busan's excellent natural harbor. It is now one of the world's busiest container ports and a major transshipment center. The city is also the southern terminus of the main railroad line from Seoul. Busan began construction on its first subway in 1980.

A leading industrial and commercial center, Busan's manufactures include ships, vehicles and vehicle parts, iron, steel, electronics, textiles, plywood, chemicals, ceramics, paper, tires and other rubber products, frozen seafood, and fishing nets. There are also important ship-repair facilities, railroad shops, and several thermal and hydroelectric power stations. Fishing and agriculture are carried on chiefly for local consumption. Nearby hot springs and coastal beaches have made Busan a popular resort city.

The city became a major port under the Chinese Empire. It was invaded in 1592 by the Japanese, who had long maintained a trading post there; however, the Japanese forces were recalled in 1598. In 1876 the Koreans were compelled to sign a treaty opening Busan to Japanese trade and immigration. In 1883 the port was opened to general foreign commerce. During the Korean War it was (Aug–Sept., 1950) the site of a United Nations beachhead (see Incheon). Refugees from the war more than doubled Busan's population. The city is the seat of a number of universities and colleges; landmarks include the Beomeo Temple.