Lee Si-eon

After graduating from high school in Busan and completing his military service, Lee Si-eon moved to Seoul.^[2] In 2005, Lee enrolled in the Broadcasting and Entertainment Department at the Seoul Institute of the Arts,^[3] joining a cohort that included Kim Seon-ho from the same department, as well as Kwon Hyuk-soo and Lee Dong-hwi from theater department.^[4]

Lee made his television debut in the 2009 drama Friend, Our Legend. He later revealed that the media had initially misreported that a female actress had been cast in his role due to his birth name, Lee Bo-yeon. The drama's director, Kwak Kyung-taek, gave him the stage name "Lee Si-eon" after consulting a naming agency. He continues to use the name throughout his career.^[5] He went on to appear in dramas such as Warrior Baek Dong-soo (2011) and The King 2 Hearts (2012).^[6]

Lee had his breakthrough with his comic supporting role as Bang Sung-jae in the tvN drama Reply 1997, the first installment of the Reply series created by Shin Won-ho and Lee Woo-jung. His character was known as the "one-man rumor mill" of the group. The series achieved both commercial and critical success, sparking a retro craze in South Korea.^{[7][8][9][10]}

Following the drama's success, on September 15, 2012, Lee, along with co-stars Seo In-guk, Eun Ji-won, and Shin So-yul, hosted an episode of Saturday Night Live Korea, which featured parodies of scenes from their series.^[11] A special program on tvN's enews was also aired on September 20, 2012, providing behind-the-scenes footage and bloopers from the set.^[12]

He also appeared in the films Tough as Iron (2013) and My Love, My Bride (2014), as well as dramas including Modern Farmer (2014), and Remember - War of the Son (2015).^[6]

In 2015, Lee expressed interest in joining the variety show Real Men, citing his experience as a drill instructor during his mandatory military service.^[13] He was subsequently invited to participate in the Real Man Manly Men special in November 2016.^[14]

Lee was cast in a supporting role in the drama W: Two Worlds, which aired on MBC from July 20 to September 14, 2016. The series explores the intersection of two realms: the real world and an alternate universe within a webtoon, from which it derives its title. Lee portrayed Park Soo-bong, an apprentice to webtoon artist Oh Seong-moo and a confidant of his daughter, Yeon-joo. W received acclaim for its innovative premise, achieving ratings of 11.63% and topping viewership ratings in its time slot throughout its run.^[15] Following the success of W, Lee joined the cast of the MBC reality show I Live Alone in September 2016.^[16][17]

He went on to appear in the dramas Man to Man (2017), Into the New World (2017), and Two Cops (2017).^[6] Lee credited I Live Alone for helping him land his role in drama Live, noting that writer Noh Hee-kyung cast him after watching him on the reality show. She had initially disliked his acting style, but after seeing him watch TV during an episode, she thought he resembled the character Kang Nam-il. Lee expressed his gratitude for the affection he received through the show, noting that it helped him show a new side of himself as an actor.^[6]

Lee has been in a relationship with actress Seo Ji-seung since 2017.^[18] On November 8, 2021, it was reported that Lee would be getting married in a private ceremony on December 25, 2021, in Jeju.^[19] Later that same day, Lee's agency confirmed the report.^[20] On May 22, 2026, the couple welcomed their first child, a son.^[21]