Yi Wŏn'gye (Korean: 이원계; Hanja: 李元桂; 1330–1388), later posthumously promoted to Grand Prince Wanp'ung, was a warrior and painter in the late Goryeo period.
In 1359 (the 8th year of King Gongmin's reign), Red Turbans invaded from the Yuan dynasty, crossing the Yalu River.
He also contributed for defeating the Red Turbans in Bakju and retook Gaegyeong during the second rebellion alongside Cho Ch'ŏn-ju (조천주) and others under general An U (안우)'s command.
He spent his old days in Wihwa-do and honoured as Prince Wansan (완산군; 完山君) while two years later after his death in 1388, he received his final title and honors for making big contribution during his lifetime.
His title was later upgraded into Count Wansan (완산백; 完山伯) and received Yangpyeong (양평) as his Posthumous name during the reign of King Taejo He was buried on the right side of Jeongneung tomb, which was also his father's tomb and was enshrined at Samui Temple (삼의사), Bukcheong in 1901 while later moved to Seonwon Temple (선원사), Yiwon, Hamgyeongnam-do in 1909 alongside his last poem.