[13] Yoo Ah-in, whose real name is Uhm Hong-sik,[14] was born in Nam District, Daegu in southeastern South Korea,[1] the youngest of three children.

[26]Resuming his acting career, Yoo starred in low-budget indie film Boys of Tomorrow, taking over the role of a young man Jong-dae, who carries the psychological scars of a traumatic childhood accident.

[36] Yoo then starred in Jeong Yoon-cheol's black comedy film Skeletons in the Closet, playing the role of an eccentric boy who believes he was a king in previous incarnation.

[45] In 2009, he was cast in romance drama He Who Can't Marry, as cheeky assistant who works at the architectural office, portraying the bright side of being in one's twenties.

[63] Yoo called the role one of the biggest challenges of his career and he garnered favorable press reviews for his mature, charismatic and versatile portrayal of Sukjong.

[57] He then played the titular character in the film Tough as Iron, about a Busan pier worker who takes care of his mother afflicted with dementia and kidney disease.

[64] Yoo and Tough as Iron co-star, Jung Yu-mi later collaborated again as voice actors in the animated film The Satellite Girl and Milk Cow.

[76][77] He played an amoral young millionaire who faces off with a detective in Ryoo Seung-wan's crime thriller/comedy Veteran with Hwang Jung-min and Yoo Hae-jin among the cast,[78][79] and as the tragic Crown Prince Sado in Lee Joon-ik's period drama The Throne alongside Song Kang-ho.

[96] In 2018, Yoo starred in Lee Chang-dong's film Burning opposite Steven Yeun, portraying a pure and sensitive young man, Jong-su, who tries to solve the mystery surrounding the woman he loves.

Justin Chang of Los Angeles Times said on NPR, "As the movie's inarticulate male lead, Yoo Ah-in has, in some ways, the trickiest task.

"[107] Pierce Conran of Screen Anarchy wrote, "Even more impressive is Yoo Ah-in, who is most well known in the West for playing the slimy son of a corporate head who serves as the villain in Ryoo Seung-wan's Veteran.

"[108] Tim Grierson of Screen Daily wrote, "Ah-in Yoo is remarkable as Burning's ineffectual, withdrawn protagonist: he's the perfect vessel for Lee's grand treatise on the immutable fact that none of us truly understands anyone or anything.

[142][143][144][145] Director Hong Eui-jeong said about the casting, "It was not easy to carry on a hardly commercial, small film, but I sent the script to Yoo Ah-in's agent and I was shocked that he responded sooner than I expected.

Nick Allen wrote for Roger Ebert, "Yoo Ah-in is excellent in this role that has him delivering cryptic words of faith with a certain deadness in his eyes.

"[173] Brian Tallerico of The Playlist was similarly positive and wrote, "Yoo Ah-in, also in the Netflix hit #Alive, is such a fascinating young actor, one who really gets what Hellbound should be about, that the show suffers when he leaves it".

[174] Polygon's Zosha Millman wrote, "Yoo Ah-in is particularly inspired casting, letting his chairman be just as virtuous as he is shifty, immovable in his low-key fanaticism.

[175] Hidzir Junaini from NME wrote, "His quiet demeanor belying an unsettling intensity, Yoo Ah-in's performance as the show's pivotal villain is creepily fascinating".

[176] In 2022, Yoo portrayed the "Sanggye-dong Supreme Team" leader in a Netflix crime comedy film Seoul Vibe with Kim Sung-kyun, Jung Woong-in and Moon So-ri among the cast.

Divya Malladi from Digital Mafia Talkies wrote, "Yoo Ah In as Dong Wook brought such a degree of believability to his character, with his blind courage that was balanced by a shrewd calculative nature.

[186][187] He will also play unemployed man with superpowers in Kang Hyeong-cheol's fantasy film Hi.5, alongside Ra Mi-ran,[188] and star in Netflix apocalyptic drama Goodbye Earth, a work based on the novel The Fool of the End by Kōtarō Isaka, directed by Kim Jin-min.

[194] Through Studio Concrete exhibitions, Yoo shows his support for the LGBT community, liberal feminist, Korean Childhood Leukemia Foundation, and other minority groups.

[121] International artists who have held their solo exhibitions in Studio Concrete are Daniel Caesar, Jean Jullien,[202] Joan Cornellà,[203] and Eric Joyner.

In January 2017, together with the renown sculptor Osang Gwon, Yoo teamed up to produce a bust-sized cubist sculpture, symbolizing the breast cancer awareness campaign "Love Your W".

[222] Considered one of the most outspoken and politically socially charged Korean actors of his generation, Yoo drew media attention in late 2012 when he tweeted a strongly worded criticism against the withdrawal of Ahn Cheol-soo from the presidential race.

"[228] In late 2017, Yoo tweeted a strongly worded criticism against the radical feminist community Megalia, which resulted in accusations that he had made aggressive expressions of a typical patriarchally minded Korean man.

"[238] Yoo has appeared in advertising campaigns for international brands, such as McCafé,[239] Diadora,[240] Diesel, Cartier, Absolut Vodka, Calvin Klein, Burberry, Birkenstock,[241][242] Burger King, and Puma.

In addition to managing Studio Concrete art gallery in Hannam-dong, Yoo had been an investor and business partner of TMI (Too Much Information), a Korean healthy fried food with mushroom-oriented restaurant in Itaewon, Seoul from 2015 to 2017.

[259] The Seoul Poets Association's magazine, Monthly Poetry, praised his writings as "beautiful, clear and clean breath of oneself that is different from glamorous life of an actor.

Yoo's representatives stated that his symptoms were benign, which meant that the non-cancerous tumor would have minimal effect on his everyday life and carry no risk of spreading.

The police performed a search and seizure of various doctors' offices and clinics in Seoul's Gangnam and Yongsan districts that are suspected of having illegally administered propofol to Yoo since early 2021.