The Korean Alphabet Day, known as Hangeul Day in South Korea, and Chosŏn'gŭl Day in North Korea, is a national Korean commemorative day marking the invention and the proclamation of the Korean alphabet (한글; 조선글), the native alphabet of the Korean language, by King Sejong the Great. It is observed on October 9 in South Korea and on January 15 in North Korea.
In South Korea, the holiday is also known as Hangeul Proclamation Day.