Mattia Gajani Billi is an Italian voice actor known for his work in dubbing anime, films, and television series. Born in Rome on December 16, 1996, he is the son of voice actor Stefano Billi. His full name is sometimes credited as Mattia Gajani Billi.

Gajani Billi is perhaps best recognized for his role as the voice of Kazuma Kuwabara in the Italian-language dub of the live-action Netflix adaptation of the anime and manga series Yu Yu Hakusho. In the realm of animation, he voiced the character Akira in the anime series Kemono Jihen. His other voice credits in animated films include a role in Le Rose di Versailles - Lady Oscar.

Beyond anime, his dubbing work spans numerous international films and television series. In live-action productions, he has provided the Italian voices for actors including Jaeden Martell in Arcadian, Richie Merritt in Clean, Jacob Collins-Levy as Eredin in The Witcher: Blood Origin, Timothy Innes as Edward in The Last Kingdom, Song Kang in the series Forecasting Love and Weather, and Shuhei Uesugi as Kazuma Kuwabara in Yu Yu Hakusho.

In addition to performing voice roles, Gajani Billi has also worked as an adapter of dialogues for the Italian dubbing of television series and cartoons, including for the series Beyond Paradise, Thank You, Next, and Kakegurui Twin.