Seoul (/soʊl/; 서울; Korean: [sʌ.ul] ( listen)), also Seul, formerly Hanseong, Keijo, and Gyeongseong, and others, – officially the Seoul Special City – is the capital and largest metropolis of the Republic of Korea (commonly known as South Korea),[2] forming the heart of the Seoul Capital Area, which includes the surrounding Incheon metropolis and Gyeonggi province, the world's 16th largest city.[11] The Seoul Capital Area houses up to half of the country's population of 50.22 million people with 678,102 international residents.[12]

Situated on the Han River, Seoul's history stretches back more than two thousand years when it was founded in 18 BCE by Baekje, one of the Three Kingdoms of Korea. It continued as the capital of Korea under the Joseon Dynasty. The Seoul Capital Area contains five UNESCO World Heritage Sites: Changdeok Palace, Hwaseong Fortress, Jongmyo Shrine, Namhansanseong and the Royal Tombs of the Joseon Dynasty.[13] Seoul is surrounded by mountains, the tallest being Mt. Bukhan, the world's most visited national park per square foot.[14] Modern landmarks include the iconic N Seoul Tower, the gold-clad 63 Building, the neofuturisticDongdaemun Design Plaza, Lotte World, the world's second largest indoor theme park,[15] Moonlight Rainbow Fountain, the world's longest bridge fountain[16] and the Sevit Floating Islands. The birthplace of K-pop and the Korean Wave, Seoul received over 10 million international visitors in 2014,[17] making it the world's 9th most visited city and 4th largest earner in tourism.[18]

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 to the world's 4th largest metropolitan economy with a GDP of US$845.9 billion[19] in 2014 after Tokyo, New York City and Los Angeles. In 2015, it was rated Asia's most livable city with the second highest quality of life globally by Arcadis.[20][21] A world leading technology hub centered on Gangnam and Digital Media City,[22] the Seoul Capital Area boasts 15[23]Fortune Global 500 companies such as Samsung, one of the world's largest technology companies, as well as LG and Hyundai-Kia. In 2014, the city's GDP per capita (PPP) of $39,786 was comparable to that of France and Finland. Ranked sixth in the Global Power City Index and Global Financial Centres Index, the metropolis exerts a major influence in global affairs as one of the five leading hosts of global conferences.[24]

Seoul is the world's most wired city[25] and ranked first in technology readiness by PwC's Cities of Opportunity report.[26] It is served by the KTXhigh-speed rail and the Seoul Subway, 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.[27] Lotte World Tower, a 556-metre (1,824-foot) supertall skyscraper with 123 floors, has been built in Seoul and become the OECD's tallest in 2016, with the world's tallest art gallery.[28][29]Its Lotte Cinema houses the world's largest cinema screen.[30] Seoul's COEX Mall is the world's largest underground shopping mall.[31]

Seoul hosted the 1986 Asian Games, 1988 Summer Olympics, 2002 FIFA World Cup, the Miss Universe 1980 pageant, and the 2010 G-20 Seoul summit. A UNESCO City of Design, Seoul was named the 2010 World Design Capital.