Colonel Prince Yi Geon (October 28, 1909 – December 21, 1991), also Ri Ken and Kenichi Momoyama (桃山 虔一, Momoyama Ken'ichi), was a Korean prince and a cavalry officer in the Imperial Japanese Army during World War II. The first son of Prince Yi Kang of Korea by Lady Jeong, he was a grandson of Emperor Gwangmu. His Korean name was Yi Geon (이건 李鍵 I Geon), and his birth name was Yonggil (용길 Yonggil).