O Yeong-su is a South Korean actor who garnered international popularity after appearing in the 2021 Netflix survival series Squid Game..His great-grandfather was a Goeul member. Goeul is an administrative division that is ruled by a chief appointed by the central government (especially during the Joseon Dynasty). His family owns a lot of land in Haeju, North Korea, and Yeong-su has the document of the land.He was born in Kaepung County, Gyeonggi, Japanese Korea. When the partition of Korea happened, his birthplace became a part of North Korea. With the formation of the 34th parallel, his family moved to Paju-si of the Gyeonggi Province, South Korea.On 25 June 1950, the North Korean communist forces invaded the South Korean borders, which caused Korean War. His father was killed by communist forced, and one of his elder brothers was abducted by the army. After the Korean War was over, his family lived in underground houses. All his siblings died due to a disease. Consequently, he did schooling, along with earning to help his mother, who used to go to a market to earn food for the family.Their condition became better after his grandfather started taking care of his family. His father used to live in Haeju, Gwanghae Province, North Korea, before the Korean War.At the age of 23, he finished his mandatory military service. One day, he went to the theater with his friend who worked at the theater company. He was awed by the reaction to the actors performing on stage, which inspired him to work at the theater. In 1967, he joined the theater troupe named Gwangjang, where he started by doing chores like cleaning and pasting posters for the theater for a year, he finally made his acting debut with the play Naj Gong-won Sanchaeg in 1968. From 1970 for some time, he worked in the theater company Seongjwa. Later, he joined the theater company Yeo-in.When he began acting in theater, he began using O Young-su as his stage name. This was because the acting was not admired at that time and was seen in a bad light.He did voice acting in educational broadcasting during the late 1970s.In 1987, he became part of the National Theater Company of Koreas theater group Jayu. He was part of the troupe till 2010, and he worked with the South Korean actor and voice actor Jang Min-ho, his idol, in the company.His wife, Mo Kang, is thirteen years younger than him. His mother-in-law did not allow Young-su and Mo Kang to get married because she thought of Young-su as a womanizer and couldnt accept their age difference. After he joined the National Theater Company of Korea in 1987, he convinced his parents-in-law that he was the right one for their daughter.