Kirk Thornton is an American voice actor, ADR director, and script writer with a career spanning several decades, primarily known for his work in English-language dubs of Japanese anime series and video games. He has been active in the voice acting industry since 1979.

Thornton's career is marked by a vast and diverse list of roles in numerous popular anime franchises. Among his most recognized performances are Brandon Heat in Gungrave, Jin in Samurai Champloo, and Hajime Saito in Rurouni Kenshin. He has a long-standing association with the Digimon franchise, voicing the character Gabumon across multiple series and films, including Digimon Adventure, Digimon Adventure tri., and Digimon Adventure: Last Evolution Kizuna. He also voices Klein, the friendly leader of a small guild, in the long-running Sword Art Online series, a role he has reprised for multiple seasons and films. Other significant roles include the cunning and ruthless Askeladd in Vinland Saga, the powerful Yujiro Hanma in the Baki series, and Kisame Hoshigaki in the Naruto and Naruto: Shippuden series. He also provided the voice for Kaname Ohgi in Code Geass, James Moriarty in Fate/Grand Carnival, and the narrator for the Bleach series.

Beyond acting, Thornton has made substantial contributions to the industry as a director and script writer. He served as a co-director and script writer for the long-running series Bleach, working alongside Wendee Lee, and also provided the narration for the show. His directorial work extends to other series such as Durarara!!×2, Blood Lad, and Kannazuki no Miko. In his early career, he was sometimes credited under pseudonyms, including Sparky Thornton, Ron Allen, and Donald Lee.

In addition to his extensive anime work, Thornton is a prominent voice in video games. He is well-known for voicing the character Saïx in the Kingdom Hearts series and both Shadow the Hedgehog and his robotic sidekick Orbot in the Sonic the Hedgehog series. His career continues to be active, with recent and ongoing roles in anime such as Demon Slayer: Kimetsu no Yaiba, Jujutsu Kaisen, and Dandadan.