Choe Sejin (1473–1542) was a Korean linguist, educator, and a proponent of hangul during the Joseon Dynasty. He is of the Goesan Choe clan and courtesy name was Gongseo (공서; 公瑞).
Choe devised the modern South Korean order of the hangul letters, and assigned names to the letters. His most famous book on hangul is the Hunmong Jahoe (훈몽자회; 訓蒙字會 "Collection of Characters for Training the Unenlightened (= Kids)", 1527).
Choe was an official interpreter in the Korean embassies in Beijing, and so he also documented colloquial northern Chinese languages (Haner).