The history of Seoul can be traced back to 18 BC and several archaeological sites in the region show traces of that first civilisation. In the early period of Seoul’s history the Three Kingdoms were fighting for hegemony in Korea and the Seoul area was often contested due to its strategic location in the Han River valley. The Joseon Period ran from 1392 up to the Japanese invasion in 1910 and Seoul was its capital. It was the longest ruling Confucian dynasty in history and during its reign the Joseon monarchy consolidated absolute rule over Korea. Just like Japan at the time of the Shoguns, Korea maintained isolation from the rest of the world for centuries and only in the late 19th century did Seoul open up to foreign influence and begin to modernize. Seoul became the first city in East Asia to have electricity, trolley cars, water, telephone, and telegraph systems all at the same time. Much of this was due to major trade with the United States.

The Japanese invaded Korea in 1910 and made Seoul its colonial capital. The period of Japanese rule lasted until the end of World War II. After World War II the liberated Republic of Korea (South Korea) came into being with Seoul once again its capital. In 1950 the Korean War broke out and Seoul changed hands between the Chinese-backed North Korean forces and the UN-backed South Korean forces several times, leaving the city heavily damaged. In addition a great many refugees entered Seoul during the war, swelling its population to an estimated 2.5 million - more than half of them homeless.

In the post-war years Seoul was the focus of an immense reconstruction and modernization effort. Today the population of the Seoul area comprises 24% of the total population of South Korea and Seoul ranks seventh in the world in terms of the number of major companies based there. Seoul hosted the 1988 Summer Olympics and was one of the venues of the Football World Cup in 2002.

In 2004 the South Korean Government came up with a highly controversial plan to relocate the capital to the Gongju area in order to ease the population pressure on Seoul and set up the seat of government at a safer distance from North Korea. The plan was finally abandoned when judged unconstitutional by the courts without a nationwide referendum.