Seoul, officially Seoul Special Metropolitan City, is the capital and largest city of South Korea. The broader Seoul Metropolitan Area, encompassing Seoul, Gyeonggi Province and Incheon, emerged as the world's sixth largest metropolitan economy in 2022, trailing 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 is the seat of the South Korean government.

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.

Seoul was rated Asia's most livable city, with the second-highest quality of life globally according to Arcadis in 2015 and a GDP per capita (PPP) of approximately $40,000. 15 Fortune Global 500 companies, including industry giants such as Samsung, LG, and Hyundai, are headquartered in the Seoul Capital Area, which has major technology hubs, such as Gangnam and Digital Media City. Seoul is ranked seventh in the Global Power City Index and the Global Financial Centres Index, and is one of the five leading hosts of global conferences. The city has also hosted major events such as the 1986 Asian Games, the 1988 Summer Olympics, and the 2010 G20 Seoul summit, in addition to three matches at the 2002 FIFA World Cup.

Seoul is geographically set in a mountainous and hilly terrain, with Bukhansan positioned on its northern edge. Within the Seoul Capital Area lie five UNESCO World Heritage Sites: Changdeokgung, Hwaseong Fortress, Jongmyo, Namhansanseong, and the Royal Tombs of the Joseon dynasty. Furthermore, Seoul has witnessed a surge in modern architectural development, with iconic landmarks including the N Seoul Tower, the 63 Building, the Lotte World Tower, the Dongdaemun Design Plaza, Lotte World, the Trade Tower, COEX, IFC Seoul, and Parc1. Seoul was named the World Design Capital in 2010 and has served as the national hub for the music, entertainment, and cultural industries that have propelled K-pop and the Korean Wave to international prominence.