Hiroyuki Yokoo is a Japanese voice actor from Osaka Prefecture, born on November 13, 1966. He is a graduate of the Faculty of Literature at Waseda University, where his involvement in a puppet theater club during his student days laid an early foundation for his performance career. He is affiliated with the talent management firm Production Baobab.

Yokoo's career as a voice actor began in the 1990s, and he has since built a diverse portfolio of roles across anime, video games, and foreign film dubbing. In anime, he is frequently cast in supporting and guest roles, contributing to a wide array of popular series. His extensive list of television anime credits includes appearances in long-running franchises such as Anpanman, Berserk, Case Closed (known as Detective Conan in some regions), Hunter × Hunter (the 2011 series), Parasyte -the maxim-, and Death Note. Specific recurring roles in Case Closed include小林 (Kobayashi) and 霧間次郎 (Kirisawa Jirō). In Hunter × Hunter, he voiced multiple characters including ソミー (Sommy), イサク (Isaku), アッサム (Assam), and サブ (Sabu). He also played the role of 牧田 (Makita) in the 1999 release Aoyama Gōshō Tanpen-shū 2.

Beyond anime, Yokoo has contributed his voice to various video games, including titles such as Guardian Heroes, the Onimusha series, and Sakura Wars 4. He is also active in the dubbing of foreign films and television dramas, with credits for Japanese-language versions of productions like ER, Criminal Minds, and Coach Carter. His work further extends to narration for channels like the World Hi-Vision Channel and other media.

A notable aspect of Yokoo's professional skill is his command of the Kansai dialect, which he often incorporates into his performances to add authenticity and regional character. His career is marked by a high degree of versatility, allowing him to portray a broad spectrum of characters, from comedic roles to serious ones, and across different age ranges.