T'aesangwang
T'aesangwang and the related title T'aesanghwang are titles used at various points in Korean history for retired king or emperors. The terms Sangwang and Sanghwang have also been used similarly.
History
Taejo of Goguryeo called himself "Taejo the Great", who is the first retired king on the Samguk Sagi to retired and abdicated in favour of his son Suseong as a successor.The last retired emperor as the T'aesanghwang was Emperor Gojong in Korean Empire.