[4][5][6] Lee Joon-gi was born in Daeyeon-dong, Nam-gu, Busan, South Korea[1] but spent his schooling years in nearby Changwon.

After finishing high school, he went against his parents' wishes for him to enter university and moved to Seoul to pursue a career in the entertainment industry.

[7] For the next several years, Lee worked at various part-time jobs such as waiting tables while auditioning for roles and also debuted as a print and commercial model in 2001.

With an average viewership rating of 20%, the romance comedy series became a hit during its run both domestically and across Asia, further catapulting Lee into Korean Wave stardom.

[32] In 2007, Lee filmed a joint Korea-Japan movie entitled Virgin Snow with Japanese actress Aoi Miyazaki, in which he plays a Korean exchange student.

[33] Virgin Snow was successful as it placed 9th at the box office chart and set a new ticket admissions record for a Korean film released in Japan.

[36][37] Prior from his previous work, the actor portrays variety of complexive emotions, successfully dispelling the 'pretty boy image' by showing off a manly short haircut in preparation for his role.

Director Kim Jin-min opined some years later that it was a turning point for Lee as the role enabled him to shed his "pretty boy" image and also highlight his martial arts background.

[39][40] From April to July 2008, Lee played the titular role in SBS's Iljimae, a period-action drama based on Chinese folklore from the Ming dynasty about a masked Robin Hood-esque character during the Joseon era.

Lee was being sued for ₩500 million for breach of contract and for supposedly hiding ₩1 billion in an attempt to "established his own agency in association with his manager".

Lee countered that he "underwent significant financial damage as the company was poor in dealing with tax affairs and profit distribution" and he is said to have notified them of contract cancellation in February.

[47][48] In February 2010, upon the expiration of Lee's contract with Mentor Entertainment, he signed with a newly established independent agency, JG Company.

[51][52] He was assigned to the public relations department of the Ministry of National Defense[53][54] He had initially applied for a postponement because he was in the midst of shooting Grand Prix with actress Kim Tae-hee, and was cast to star in television drama Faith.

[56] In August, Lee co-starred with fellow actor Ju Ji-hoon in military musical, Voyage of Life to commemorate the 60th anniversary of the Korean War.

[58][59] After serving 21 months of active duty, Lee was discharged on 16 February 2012 from the Defense Media Agency at Yongsan-dong, Yongsan District, Seoul.

[68][69] In 2013, Lee starred in the action thriller Two Weeks, playing a father struggling to save his daughter from leukemia while fighting a murder charge.

[74][75][76] The drama topped the ratings for its time slot and also garnered attention overseas, especially in China where it surpassed 200 million views in a month on Tencent QQ's video-viewing platform.

[85] The production was not well received domestically,[86] but averaged 100 million cumulative views per episode during its simulcast on the Chinese video hosting site Youku and led to a rise in popularity for Lee in China.

[102] In 2020, Lee was cast in the tvN thriller melodrama The Flower of Evil, reuniting him with Criminal Minds co-star Moon Chae-won.

"[24] Lee Joon Gi's acting is characterized by his effective use of facial expressions and body language to convey the essence of each character he portrays.

Due to his proficiency in taekwondo and several other forms of martial arts, he rarely uses a stunt double for fight scenes[114][115] and is recognized within the industry as one of the country's top action stars.