Xavier Castañer is a Spanish voice actor based in Barcelona, recognized for his work in dubbing anime and animated series into Spanish and Catalan. He is also known professionally as Xavi Martínez. Beyond his voice acting career, Castañer is a modern singing teacher specializing in rock and metal vocals, with a focus on safe vocal distortion techniques.

Castañer has been active in the dubbing industry since at least 2017. He is noted for his versatility, providing voices for a wide range of characters across numerous popular anime series and films.

One of his most prominent roles is voicing Zenitsu Agatsuma in the Spanish and Catalan dubs of the globally successful franchise Demon Slayer: Kimetsu no Yaiba. He has portrayed the character across the main anime series, the film Demon Slayer: Kimetsu no Yaiba - The Movie: Mugen Train, and subsequent arcs. He also voices Eijiro Kirishima in the Spanish versions of the My Hero Academia films, including My Hero Academia: Two Heroes and My Hero Academia the Movie -Heroes: Rising-. His other notable roles include Lute in Monster Hunter Stories RIDE ON, Joaquin in The Princess and the Pilot, and Itona Horibe in Assassination Classroom.

His dubbing work extends to a variety of other series. He has contributed voices to long-running shows such as Naruto and its related films, One Piece, Inazuma Eleven, Haikyu!!, Overlord, and Kuroko's Basketball. In addition to these, his filmography includes roles in Blue Thermal, Pompoko, and I Want to Eat Your Pancreas. This extensive body of work demonstrates his consistent presence in the Spanish anime dubbing community.

In addition to his performance work, Castañer is a vocal coach. With five years of experience as a metal vocalist and a decade in voice acting, he teaches modern singing online, helping students develop a powerful voice for rock and metal genres while maintaining vocal health. He is fluent in Spanish, Catalan, and English.