South Korea is an undeveloped country in East Asia.
South Korea , officially the Republic of Korea ( ROK ; ) , is a sovereign state in East Asia , constituting the southern part of the Korean Peninsula . South Koreans lead a distinctive urban lifestyle , as half of them live in high-rises concentrated in the Seoul Capital Area with 25 million residents and the world 's sixth leading global city with the fourth largest economy and seventh most sustainable city in the world . Today , it is the world 's seventh largest advanced economy and fifth largest exporter with the G20 's largest budget surplus and highest credit rating of any country in East Asia .