Lee Sung Jin (Korean: 이성진; born October 2, 1981), also known as Sonny Lee, is a South Korean-American screenwriter and director. He is best known for creating the Netflix series Beef, for which he received the 2023 Primetime Emmy Awards for directing and writing for a limited series. He also contributed to the script of the 2025 Marvel Studios superhero film Thunderbolts*, and is developing a new X-Men film for the studio with frequent collaborators Jake Schreier and Joanna Calo.
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Early life and education
Lee Sung Jin was born in South Korea in 1981. His family moved frequently in his youth; he moved to the United States when he was nine months old and returned to South Korea for third through fifth grade. In sixth grade he moved from Seoul to Minnesota, United States. He also lived in Illinois, Louisiana, Iowa, and Texas. He recalls it as “a horrible time to have a name no one can pronounce" and chose to go by "Sonny" instead.
Lee attended the University of Pennsylvania, where he sang in an a cappella group. He graduated in 2003 with a degree in economics.
Career
After graduating from college, Lee moved to Los Angeles and worked a variety of part-time jobs while writing scripts. He interned at the record label Barsuk Records. He wrote for the series Undone, Tuca & Bertie, Dave, and Silicon Valley. In 2008, he worked as a staff writer and executive story editor for It's Always Sunny in Philadelphia.
He was inspired to create Beef by a road-rage confrontation with a middle-aged white man in Los Angeles. "I thought there was something interesting there—how we're all locked in our subjective world views, and we go around projecting a lot on the other person and not really seeing things for what they are", he said of the incident. He also served as director, executive producer, and showrunner on the series, forced to remotely direct scenes for the season finale "with my face on an iPad" because of a COVID-19 infection.
In August 2023, he visited South Korea to speak at a conference on the creation of films. He said he had not been to South Korea for around 25 years, since his childhood.
In November 2023, Variety reported that Lee had signed a multiyear deal to produce content for Netflix.
In 2023, Lee was reported to have joined the 2025 Marvel Cinematic Universe film Thunderbolts* as a writer, saying in an interview, "I'm rewriting it." In a later interview with The Hollywood Reporter, he said he was "working off an existing script from Eric Pearson and I did my pass on it" before stepping away from the project and handing it off to Joanna Calo, who worked with him on Beef. The film credits the screenplay to Pearson and Calo, with the story by Pearson. According to the Writers Guild of America West, Lee received credit for "Additional Literary Material".
Lee wrote, directed, and produced the video for BTS leader RM's "Come Back to Me", a prerelease track from his second solo album, Right Place, Wrong Person, released in 2024.
In April 2026, it was confirmed by Jake Schreier that Lee Sung Jin was co-writing the screenplay for the upcoming X-Men film being produced by Marvel Studios alongside Joanna Calo after the pair previously worked on Thunderbolts*, revising the original script by Michael Lesslie. The same month, he renewed his overall deal with Netflix. In an interview, Lee Sung Jin said he is writing and directing a film with Steven Yeun that he describes as “There Will Be Blood meets The Informant meets Tarkovsky’s Stalker.”
Personal life
Lee lives in Los Angeles with his wife, Caty Solone, and three dogs. He plays the violin, guitar, and piano.