Seoul is the capital and largest city of South Korea. With over 11 million people, Seoul is the 5th largest city in the world, with an area of only 234 square miles, it is also one of the smallest and most densely populated major cities. Seoul's population density has allowed it to become one of the world's most digitally-connected cities. It also has more than three million registered vehicles which often cause widespread traffic jams.

The larger Seoul area and commuter belt, which includes the major port city of Incheon, has over twenty-one million residents. This makes it the third most populous metropolitan area in the world, after Greater Tokyo and Mexico City. About one-half of South Korea's entire population live in Seoul and its environs. The city is the country's political, cultural, social, and economic center, as well as an international center for many financial and business organizations, and is considered one of the top 20 "world-class cities".