is a Japanese film director and screenwriter. An alumnus of the University of Tokyo and the Tokyo National University of Fine Arts and Music, he started gaining attention in his home country with the graduate film Passion (2008).

Hamaguchi first gained international recognition with the film Happy Hour (2015) and continued with Asako I & II (2018). In 2021, he released two films, Wheel of Fortune and Fantasy and Drive My Car; for the latter he received two Academy Awards nominations, for Best Director and Best Adapted Screenplay. He is the third Japanese director to be nominated for an Oscar for Best Director.

After graduating from the University of Tokyo, Hamaguchi worked in the commercial film industry for a few years before entering the graduate program in film at Tokyo University of the Arts where he studied with and was influenced by Kiyoshi Kurosawa. His graduation film Passion was selected for the competition of the 2008 Tokyo Filmex.

With Kō Sakai, he made a three-part documentary about survivors of the 2011 Tōhoku earthquake and tsunami, with Voices from the Waves being selected for the competition at the 2013 Yamagata International Documentary Film Festival, and Storytellers winning the Sky Perfect IDEHA Prize.

His next film, Happy Hour, was first developed while Hamaguchi was an artist in residence at KIITO Design and Creative Center Kobe in 2013. It came out of an improvisational acting workshop he held for non-professionals, with many of the film's performers having participated in the workshop. The four lead actresses shared the best actress award and the film earned a special mention for its script at the 2015 Locarno Film Festival. Hamaguchi was also given a special jury award at the 2016 Japan Movie Critic Awards, as well as a best newcomer award in the film division of the Agency for Cultural Affairs' Geijutsu Sensho Awards that year.

His Asako I & II was selected to compete for the Palme d'Or at the 2018 Cannes Film Festival.

In 2021, Hamaguchi won the Silver Bear award at the Berlinale with his Wheel of Fortune and Fantasy. That same year his Drive My Car won Best Picture awards from the New York Film Critics Circle, Boston Society of Film Critics, and Los Angeles Film Critics Association as well as "Best Motion Picture - Non-English Language" at the Golden Globes. Hamaguchi was nominated for an Oscar for Best Director for Drive My Car, becoming the third Japanese director to accomplish this feat.

In 2023, his film Evil Does Not Exist was awarded the Grand Jury Prize at the Venice Film Festival.