Foreign nationals entering Korea are generally required to have a valid passport and a Korean visa assigned by overseas branch of Korean embassy or consular offices. However, many are now permitted visa-free for a limited period under certain conditions. South Korea maintains a visa waiver agreement list  and a designated visa-free entry list  with countries not included on those lists requiring a visa to enter the country . In addition, foreigners wishing to engage in certain activities such as diplomatic work, gainful employment, study or residence must apply for the appropriate visa prior to engaging in that activity in country.
In order to check whether you're allowed to enter Korea without visa issuance and for other requirements, please contact the Korean immigration offices or visit the following websites to confirm:
* Wikipedia page: en.wikipedia.org/wiki/Visa_policy_of_South_Korea
* Ministry of Foreign Affairs : www.mofa.go.kr/ENG/main/index.jsp
* Korea Immigration Service : www.immigration.go.kr/HP/IMM80/index.do
* Hi Korea (e-government for foreigners) : www.hikorea.go.kr/pt/main_en.pt