What is the capital of South Korea?

The capital of South Korea is Seoul. This city serves as the political, economic, and cultural center of the country. It is one of the largest cities in the world and has a significant historical background dating back over 2,000 years. As the capital, Seoul is home to major government institutions, including the Presidential Office, as well as numerous cultural landmarks and institutions that represent South Korea's heritage.

Busan, another major city, is known for its port and beaches but is not the capital. Incheon is recognized for its international airport but also does not hold the status of the capital. Gwangju is known for its historical significance and cultural contributions but is similarly not the capital. Therefore, Seoul is the unequivocal answer to the question regarding the capital of South Korea.