Why South Korea built Sejong

A capital blocked by custom

About half of South Korea’s 51 million people live in and around Seoul, and the capital region produces 53 percent of the country’s GDP on 12 percent of its land.^[2] Campaigning in 2002, Roh Moo-hyun promised to move the presidential Blue House and the ministries to the Chungcheong region to curb that concentration. He won, and a special act to build a new administrative capital was promulgated on 16 January 2004.^[3]

Citizens challenged it, and on 21 October 2004 the Constitutional Court struck the act down by 8 votes to 1. The constitution nowhere says Seoul is the capital, the court said, but six centuries of practice since the Joseon dynasty made it an unwritten constitutional custom, so moving the capital would need a constitutional amendment.^[3]

“There is no express provision in our Constitution that states ‘Seoul is the capital.’ However, that Seoul is the capital of our nation is a continuing practice … for a period of over six-hundred years since the Chosun Dynasty period.”^[3]

An administrative city instead

In 2005 the government announced a new plan: a “multifunctional administrative city” about 130 km south of Seoul, on land taken from Gongju and Yeongi County, to take about two-thirds of the government’s offices.^[1] A naming committee chose Sejong, after the 15th-century king who introduced the Hangeul alphabet, and the Sejong Special Self-Governing City was launched on 1 July 2012.^[1]

Ministries followed. By 2026, 44 central government bodies had moved, including the finance and health ministries.^[2] But the law that created the city does not make it the country’s administrative capital.^[5]

Bringing the president

The president never had a real base among the relocated ministries.^[4] President Yoon Suk Yeol’s government planned a second presidential office in Sejong, and during his impeachment trial in early 2025 calls grew to make it the main one; critics warned that would reopen the question of moving the capital.^[5]

Lee Jae-myung promised in April 2025 to build a presidential office in Sejong within his five-year term, and after winning the election he made it a fast-track priority. Because a full move would need a constitutional amendment, it is planned as a second workplace alongside Seoul.^[4] In September 2026 the government set targets of August 2029 for the presidential office and 2033 for a second National Assembly building, and said the foreign and unification ministries could follow.^[2]