If you are a citizen of a country which has a visa exemption agreement with Korea, you can enter Korea without a visa.

Here are the countries designated by Korean government under Visa-waiver agreement: https://english.visitkorea.or.kr/enu/TRV/TV_ENG_2_1.jsp

Please note that due to the COVID-19 situation, policies related to visa free entry may change under specific conditions. (According to Korean government, visa-waiver program from 16 countries or regions temporarily suspended since April 1 , 2022)