Matthias Keller is a German voice actor, speaker, musician, and singer, recognized for his extensive work in dubbing foreign films and television series, as well as for his contributions to radio, audiobooks, and video games. Born in Frankfurt am Main in 1970, he began his professional career as a self-employed voice artist in 1995 and has since become a prominent figure in the German voice-over industry. His versatility is a hallmark of his work, allowing him to transition between authoritative commercial voiceovers, character-driven narration in audiobooks, and comedic roles in radio plays.

Keller is widely known for providing the German voice for numerous characters in anime series. He is most notably the German voice of Seijirou Kikuoka, also known by his in-game handle Chrysheight, across the entire Sword Art Online franchise. This includes the roles in Sword Art Online, Sword Art Online II, the film Sword Art Online: The Movie - Ordinal Scale, and the Alicization arcs, including Sword Art Online: Alicization and Sword Art Online: Alicization - War of Underworld. Another significant anime role is Kureha Shinogi in the Grappler Baki Maximum Tournament series. Beyond these, his anime dubbing work is extensive and includes the role of the sentient uniform Senketsu in Kill la Kill, the voice of Berserker / Lancelot in the Fate/Zero and Fate/stay night: Unlimited Blade Works series, Van Argiano in Blood+, Gin'ei Morioka in Rosario + Vampire and its sequel, and Tomoya Seo in Assassination Classroom.

Throughout his career, Keller has developed recurring collaborations with specific Japanese voice actors, becoming a standard German voice for their performances. He is frequently cast as the German voice for Toshiyuki Morikawa, which includes his role as Seijirou Kikuoka in the Sword Art Online series. Similarly, he regularly lends his voice to characters originally voiced by Ryoutarou Okiayu, such as Lancelot in the Fate series. His repertoire also includes providing the German voice for Tomokazu Seki's roles, like Gin'ei Morioka in Rosario + Vampire, and for Toshihiko Seki, including the role of Senketsu in Kill la Kill.

In addition to his anime work, Matthias Keller has a broad career that spans various media. He is the station voice for the German radio station hr1. He is also the narrator for the German Winnie Puuh audio plays by Walt Disney. In the realm of video games, he is renowned for voicing Leon S. Kennedy in the 2019 and 2023 remakes of Resident Evil 2 and Resident Evil 4, as well as in the animated series Resident Evil: Infinite Darkness. He also took over the main role of Rico Rodriguez from Moritz Bleibtreu for the fourth installment of the Just Cause video game series.

Keller's work has also received critical recognition. In 2012, he performed a live radio play adaptation of Charles Dickens' A Christmas Carol with the NDR Radiophilharmonie, and the resulting CD was awarded the Deutsche Kinderhörbuchpreis (German Children's Audiobook Award). His creative output extends to live performance with his solo program Loopinsland, where he uses a loop station to create complex soundscapes and songs solely with his voice. He is also a member of the a cappella band U-Bahn Kontrollöre in tiefgefrorenen Frauenkleidern.