Born in 1973 in Ishikawa-ken, Japan, Hiromasa Yonebayashi studied Commercial Design at the Kanazawa College of Art. In 1996 Yonebayashi joined Studio Ghibli and worked as an “in-between” animator on Princess Mononoke (1997) and My Neighbors the Yamadas (1999), and as Key Animator for Spirited Away (2001), “The GHIBLIES Episode 2” (2002), Howl’s Moving Castle (2004), and Ponyo (2008). He was also the Assistant Supervising Animator for Tales from Earthsea (2006).

Yonebayashi has also worked on short films for the Ghibli Museum, Mitaka. He was the Director of Animation for the “Mei and the Baby Cat Bus” (2002), the Supervising Animator for “Imaginary Flying Machines” (2002), and also storyboarded and directed “Evolution” (2008), a short film documenting the “Films Go Round” exhibit.

Yonebayashi made his debut as the director of a feature-length animated film with Studio Ghibli's production Arrietty. After Arrietty, Yonebayashi directed another Ghibli movie, When Marnie Was There (2014), then left the studio and made Mary and the Witch’s Flower for Studio Ponoc.