Choe Je-u, who used the pen name Su-un, (18 December 1824 – 15 April 1864) was the founder of Donghak, a Korean religious movement against foreign invasions and critical of Joseon Dynasty government policies of the time. His teachings led to peasant revolts in Korea which were contemporary with the Taiping Rebellion in China, and he was martyred by order of the Daewongun, only weeks before the death of Hong Xiuquan.
His birth-name was Choe Je-seon ("save and proclaim"). During his childhood, he was also called Bok-sul ("blissfully happy"). He took the name Je-u ("saviour of the ignorant") in 1859. His disciples called him Su-un ("water cloud"), which was the name he used for his writings, and also called him Daesinsa, the great teacher.