Chang Yŏngsil

Chang Yŏngsil (Korean: 장영실; Hanja: 蔣英實; pronounced [t͡ɕɐŋ jʌŋɕiɭ]; ? – after 1442) was a Korean mechanical engineer, scientist, and inventor during the Joseon dynasty. He was born to a mother who was a government-registered courtesan (관기; 官妓) and a father of Yuan dynasty descent. Although Chang was born a nobi (slave), King Sejong gave him a court-technician position in the royal court.

Chang's inventions, such as the ch'ŭgugi (the rain gauge) and the water gauge, highlight the technological advancements of the Joseon dynasty.