Jeju-do ( translated Korea for Jeju Province ) is the largest island of South Korea . Jeju-do ( transliterated Korean for Jeju Province , short form of Jeju Special Autonomous Province ) is the only special autonomous province of South Korea , situated on and coterminous with the country 's largest island . Jeju-do lies in the Korea Strait , southwest of Jeollanam-do Province , of which it was a part before it became a separate province in 1946 .