Yi Sung Soon (이성순, 李聖淳, February 29, 1916 – February 25, 1983), nicknamed Lynx, was a South Korean street knight. He was born in 1916, in the North Korean city of Sinuiju.
In July 1945, Yi's friend was half dead after an attack by 40 Japanese gang members. After the independence of Korea, Yi ran away to South Korea to join with his gangster friend Yi Hwa-ryong's gangs of Myeongdong. After the Korean War broke out, Yi worked in the Headquarters of the Intelligence Detachment. In 1953, the political hoodlum Yi Jung-jae lured Yi out and lynched him, making him Yi disabled. Yi left the gangs, and escorted Chang Myon and Shin Ik-Hee from political hoodlums.