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 onPrincess Mononoke(1997) andMy Neighbors the Yamadas(1999), and as Key Animator forSpirited Away(2001), The GHIBLIES Episode 2 (2002),Howls Moving Castle(2004), andPonyo(2008). He was also the Assistant Supervising Animator forTales 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 productionArrietty. AfterArrietty,Yonebayashi directed another Ghibli movie,When Marnie Was There(2014), then left the studio and made Mary and the Witchs Flowerfor Studio Ponoc.