Marta Sáinz is a highly regarded Spanish voice actress, celebrated for her extensive and influential work in dubbing anime into Spanish. Born in 1966, she is considered one of the most veteran and versatile female dubbers in the Spanish anime industry, with a career that began in the era when Japanese series first became a staple on public television during the 1990s.

Her career in dubbing started with work for the television channel Telecinco, but her breakthrough role arrived when distributor Arait Multimedia brought the series Slayers to Spain. Sáinz was cast as the protagonist, Lina Inverse, a character who became her signature role and established her as a go-to voice for energetic and outgoing heroines. This role showcased her ability to lead a series and demonstrated her versatility, as the limited cast size for the Spanish dub meant she also voiced other characters in the same show, such as Sylphiel.

Throughout her prolific career, Sáinz has lent her voice to a vast array of iconic characters. She has played the lead in numerous major franchises, including Usagi Tsukino in the Sailor Stars season of Sailor Moon, Lum in Urusei Yatsura, and Hiromi Oka in Aim for the Ace!. Her work within the Digimon franchise is particularly notable; she voiced multiple key characters across different series, including Sora Takenouchi, Gatomon, and Davis Motomiya in Digimon Adventure and Digimon Adventure 02, as well as Zoe Orimoto in Digimon Frontier. Her role as Davis Motomiya stands as a prime example of her occasional work in cross-dressing voices, where she voices a male character. Other significant anime roles include Aisa and Muret in One Piece, Ayumi Yoshida in Case Closed, Hana in Ojamajo Doremi, Remi in Ie Naki Ko Remi, and Rita Rossi in Ashita no Nadja, among many others.

Sáinz's recognizable voice is known for its deceptive versatility, allowing her to portray a wide spectrum of characters, from protagonists and energetic girls to boys and even antagonists, often within the same series. Beyond anime, her work extends to dubbing live-action films and television series, where she is one of the Spanish voices frequently associated with actress Naomi Watts. Her contributions to bringing anime to Spanish-speaking audiences have made her a beloved and respected figure in the industry, with a career that includes a remarkably high number of leading roles. She has also been involved in promoting anime culture, having worked as a reporter for the Cuatrosfera Otaku block on the Spanish television channel Cuatro.