Mafalda Luís de Castro is a Portuguese actress and voice actress, born in Lisbon on August 12, 1989. She is recognized for her work in television, film, and particularly for her extensive contributions to dubbing in European Portuguese. A notable example of her voice work in animation is the character Ocho in the "Lop & Ocho" episode of the anime series Star Wars: Visions.

Her career began in the early 2000s with roles in Portuguese television series such as Olhos de Água and Um Estranho em Casa. She gained prominence through various television roles, including a leading part in the series Lua Vermelha. Alongside her on-screen acting, de Castro built a substantial career in voice dubbing. One of her most prominent roles is providing the European Portuguese voice for Hermione Granger in the first four Harry Potter films and their related video games. This work extended to dubbing for animated films and series, where she voiced characters such as Princess Pea in The Tale of Despereaux, Sam O'Hare in Hop, Gidget in The Secret Life of Pets, Eep in The Croods, and Blossom in the 2016 version of The Powerpuff Girls, among many others.