Ahn Yeon-seok lived in Seoul until he was six years old and his family moved to the South Gyeongsang Province because his father, a professor of selenodesy, was posted at a national university there. In his junior year in high school he decided to take up acting, so he followed his brother, who was studying another year to enter university, to Seoul and they lived together near the district of Samseong-dong.While taking acting classes, the high schooler met a friend who would later work on the costume staff of film director Park Chan-wook. Remembering that he resembled actor Yoo Ji-tae, she gave him a call about auditioning for a role. So without having to pass out his resume, he made his acting debut as Yoo's younger counterpart in the acclaimed 2003 film Oldboy. Upon graduation from Sejong University with a degree in Film Arts, he resumed his acting career in 2008. At his agency's recommendation, he began using the stage name Yoo Yeon-seok. He took on supporting roles on television, such as the haughty student body president in the horror series Soul and more appealing characters in medical drama Midnight Hospital and Tasty Life. But Yoo received his best reviews yet for playing a sensitive ex-boyfriend searching for his child in indie Re-encounter.Soon after he became known to mainstream audiences as the rich and spoiled antagonist in the box office hit melodramas Architecture 10, and A Werewolf Boy.He further raised his profile in 2013, with comedy film Born to Sing and the fantasy series Gu Family Book. Yoo's recently-completed project was the nostalgic campus drama Reply 1994, his first leading role on television.