Seoul is the capital and largest metropolis of South Korea, forming the heart of the Seoul Capital Area, which includes the surrounding Incheon metropolis and Gyeonggi province, the world's second largest metropolitan area with over 25.6 million people. It is home to over half of South Koreans along with 678,102 international residents.[6] With a population of over 10 million, the megacity is the largest city proper in the OECD.

Today, Seoul is considered a leading and rising global city, resulting from an economic boom called the Miracle on the Han River which transformed it from the damage of the Korean War to the world's 4th largest metropolitan economy with a GDP of US$774 billion in 2012 after Tokyo, New York City and Los Angeles. A world leading technology hub centered on Gangnam and Digital Media City, the Seoul Capital Area boasts 15 Fortune Global 500 companies such as Samsung, the world's largest technology company, as well as LG and Hyundai-Kia. In 2013, the city's GDP per capita (PPP) of $39,448 was comparable to that of France and Finland. Ranked sixth in the Global Power City Index and eighth in the Global Financial Centres Index, the metropolis exerts a major influence in global affairs as one of the five leading hosts of global conferences. Seoul ranked seventh in the Sustainable Cities Index, the highest in Asia and ranked second worldwide in the social category. It also hosts the world's most art openings per square mile.

Seoul is the world's most wired city and ranked first in technology readiness by PwC's Cities of Opportunity report. Its transportation infrastructure is ranked as the best in the Northern Hemisphere in the Sustainable Cities Index. It is served by the KTX high-speed rail and the Seoul Subway, the world's largest subway network, providing 4G LTE, WiFi and DMB inside subway cars. Seoul is connected via AREX to Incheon International Airport, rated the world's best airport nine years in a row (2005–2013) by Airports Council International. Lotte World Tower, a 556m (1,824 ft) supertall skyscraper with 123 floors, is being built in Seoul to become the OECD's tallest in 2015 with the world's tallest observation deck and art gallery. Its Lotte Cinema houses the world's largest cinema screen. Seoul's COEX Mall is the world's largest underground shopping mall. Emporis ranked Seoul's skyline having the world's fourth highest visual impact among major cities.