Marshall, who also appeared in The Grim Adventures of Billy and Mandy, will take over the role from The Boxtrolls and Sonic Boom actress Nika Futterman, who played the role on Disney XD's Ultimate Spider-Man.
For the handful of readers who didn't watch last year's blockbuster film adaptation of the Guardians of the Galaxy, Gamora is the adoptive daughter of Thanos, the Mad Titan. She's genetically-engineered to be one of the most dangerous individuals in the universe and sometimes finds herself feeling somewhat isolated from her teammates as a result.
Marshall is no stranger to playing kick-ass women; in addition to playing Hera Syndulla on Star Wars Rebels, she portrayed Wonder Woman in both the Infinite Crisis video game and Justice League: The Flashpoint Paradox. She's also played DC Comics' Black Canary, Poison Ivy, Galia and The Huntress in various projects, and Marvel's Black Widow, Mary Jane Watson and Jean DeWolfe.
The Guardians of the Galaxy Animated Series is expected to premiere on Disney XD in 2015.