Juan Alfonso Arenas is a Spanish voice actor and ADR director known for his work in dubbing anime and live-action productions for Spanish audiences, particularly for Netflix-distributed versions. He is notably recognized as the Spanish dub voice of Barnaby Brooks Jr. in the superhero series Tiger & Bunny and its sequel Tiger & Bunny 2. His other significant anime voice roles include Chang Gai Steiner in the time-travel science fiction series revisions, Noppo in the comedy series Dino Girl Gauko, Taku Morisaki in the Studio Ghibli film Ocean Waves, and Seiji Amasawa in the Studio Ghibli film Whisper of the Heart.

Beyond these performances, Arenas's dubbing portfolio includes the character Howzer in The Seven Deadly Sins and its related series, Lune in The Cat Returns, and Saeki in Ultraman. He has also lent his voice to Spanish dubs of live-action films, such as the role of Kamek in The Super Mario Bros. Movie. In addition to voice acting, Arenas has worked as an ADR director, overseeing the Spanish dubbing for several Studio Ghibli films, including The Cat Returns, Ocean Waves, and Whisper of the Heart for their Netflix releases.