João Vieira is a Brazilian voice actor recognized for his work in dubbing anime for Portuguese-language audiences. He has built a career portraying a wide variety of characters, ranging from energetic and comedic figures to more serious and iconic leads.

Vieira is particularly known for several prominent roles in popular anime series. He voices the enthusiastic and loyal Gobta in the long-running series That Time I Got Reincarnated as a Slime, as well as its spin-off, The Slime Diaries. In the mystery series Shadows House, he takes on the dual role of John and his living face, Shaun, for both the first and second seasons. He also portrays the skilled sniper Ukyo Saionji in Dr. Stone: Stone Wars and the special Dr. Stone: Ryusui.

Beyond these roles, his filmography includes voicing the antagonist Majima in Lycoris Recoil and Mohammed Ali Jr. in the Baki series. He is also the voice of Free De La Hoya in Beyblade Burst Sparking and other Beyblade Burst installments. A significant role in his career is providing the Portuguese voice for the protagonist Kazuto "Kirito" Kirigaya across multiple entries in the Sword Art Online franchise, including the Alicelysation arcs and the Progressive film Aria of a Starless Night. His other voice credits include appearances in series such as Kono Oto Tomare!: Sounds of Life, Fate/Apocrypha, and Violet Evergarden.

In addition to his work as a voice actor, João Vieira has also contributed to the industry as an ADR director. He served as the director for the Portuguese dubs of both seasons of Kono Oto Tomare!: Sounds of Life and for Shadows House, showcasing his broader involvement in the localization process.