Seoul

Seoul, officially Seoul Special Metropolitan City, is the capital and largest city of South Korea, and the largest city in the whole of Korea. The broader Seoul Metropolitan Area, encompassing Seoul, Gyeonggi Province and Incheon, emerged as the world's sixth largest metropolitan economy in 2022, behind New York, Tokyo, Los Angeles, Paris, and London, and hosts more than half of South Korea's population. Although Seoul's population peaked at over 10 million, it has gradually decreased since 2014, standing at about 9.6 million residents as of 2024.

Seoul's history traces back to 18 BC when it was founded by the people of Baekje, one of the Three Kingdoms of Korea. During the Joseon dynasty, Seoul was officially designated as the capital, surrounded by the Fortress Wall of Seoul. In the early 20th century, Seoul was occupied by the Empire of Japan, temporarily renamed "Keijō" ("Gyeongseong" in Korean). The Korean War brought fierce battles, with Seoul changing hands four times and leaving the city mostly in ruins. Nevertheless, the city has since undergone significant reconstruction and rapid urbanization.

The de facto administrative capital has gradually switched to the planned city of Sejong City, which opened in 2012 and is located about 121 kilometers further south. As of 2019, Sejong hosts 10 out of the South Korean government's 18 ministries. Despite this, the Constitutional Court of Korea declared in 2004 that Seoul must remain the national capital due to it being an "unwritten constitutional custom", unless otherwise changed by a nationwide referendum.