Mirren has been cast to play the villainous Hespera in forthcoming Shazam! Fury of the Gods, ET has learned.
"I am privileged to join the team of incredible artists who join together to create the wonder world of Shazam!" the 75-year-old actress told ET exclusively. "And it was my step son's favorite as a kid. We have family photos of him dressed as Shazam from 42 years ago!"
Mirren's character is a bit of a mystery for fans, as Hespera, the daughter of the god Atlas, does not appear in the comics. She is reportedly having an antagonistic relationship with the film's eponymous hero.
In the film, young Billy Batson (Asher Angel) is imbued with magic powers and turns into an adult superhero (played by Zachary Levi) when he shouts the magic word, "SHAZAM!"
The key phrase is actually an acronym for several different gods of Greek mythology, and grants the hero with the wisdom of Solomon, the strength of Hercules, the stamina of Atlas, the power of Zeus, the courage of Achilles and the speed of Mercury.
Director David F. Sandberg is returning to helm the sequel, which will also reunite most of the original cast and screenwriter, Henry Gayden.
Also reportedly joining the cast is Rachel Zegler, who, according to The Hollywood Reporter, will play Mirren's mythological sister.
Mirren, meanwhile, has established an impressive reputation for taking on splashy roles in high-octane action flicks, including RED, Fast & Furious Presents: Hobbs & Shaw and the upcoming F9.