[4] Aside from his acting career, Lee is also a businessman, having launched a chain of restaurants in Seoul, as well as founding several businesses including the development company Seorim C&D.

[5][6] Born in Seoul, Lee debuted as a fashion model, then began his acting career on television, notably in the drama Sandglass (1995).

In 2021, Lee gained widespread international stardom and fame for his role as Seong Gi-hun, the main protagonist of Netflix's survival drama Squid Game.

Upon making his acting debut with the 1993 TV drama Dinosaur Teacher, Lee became a star practically overnight, and was almost always cast in lead roles thereafter.

A year later, he received favorable reviews for his first big screen role in Bae Chang-ho's The Young Man, but it was the 1994 hit campus drama Feelings that made him a household name.

[13] In 1995, what was supposed to be a small supporting role as the heroine's silent, devoted bodyguard in ratings behemoth Sandglass turned Lee into a national heartthrob, such that his screen time was increased throughout the series' run.

[19] Lee's much-anticipated return to television a decade after his memorable turn in Sandglass (1995) was not successful ratings-wise; Air City (2007) and Triple (2009).

[20][21] With the period action comedy The Accidental Gangster and the Mistaken Courtesan, Lee said he wanted to try his hand at playing a different kind of role, a comical loose cannon type of character.

[27] As his next project, he joined the star-studded ensemble cast of The Thieves, a 2012 heist film that became the second all-time highest-grossing movie in Korean cinema history.

[23][28][29][30][31] El Fin del Mundo ("The End of the World") is a 13-minute split screen film made by visual artists Moon Kyung-won and Jeon Joon-ho, which depicts the destructive environmental changes the world faces in the future and the subsequent end of art and birth of new art based on dialogue between two artists in different times and space, played by Lee and Im Soo-jung.

[41] He later signed on to be exclusively managed by C-JeS Entertainment, reportedly choosing the agency after he worked with Song Ji-hyo in New World.

[43][44] This was followed by the action comedy Big Match in 2014, where he played a mixed martial arts fighter trying to save his brother by winning an elaborate high-stakes game.

[45][46][47] In 2015, he reunited with The Thieves director Choi Dong-hoon and actress Jun Ji-hyun in Assassination, set in 1930s Korea and Shanghai during the Japanese occupation.

[59] In September 2021, Lee starred as Seong Gi-hun, the main protagonist of Netflix's hit survival drama Squid Game.

Series creator and director Hwang Dong-hyuk said he chose to cast Lee as Gi-hun as to "destroy his charismatic image portrayed in his previous roles".

On June 29, Netflix released more info on the new season's cast, which includes Kang Ha-neul, Park Sung-hoon, Im Si-wan, Yang Dong-geun, Park Gyu-young, Lee Jin-wook, Won Ji-an, Jo Yu-ri, Kang Ae-shim, Choi Seung-hyun, Lee David, and Roh Jae-won.

[16][80] Lee also founded the real estate development company Seorim C&D in 2008,[81] and owns several businesses with actor Jung Woo-sung, a close friend whom he first worked with on the film City of the Rising Sun.

[83] On March 8, 2022, Lee additionally donated ₩100 million to the Hope Bridge Disaster Relief Association along with Jung Woo-sung to help the victims of the massive wildfire that started in Uljin, Gyeongbuk and had spread to Samcheok, Gangwon.