The casting was confirmed Thursday by famed comic book writer and DC Entertainment president and chief creative offiicer Geoff Johns while speaking with The Wall Street Journal.
Johns, who is helping Affleck craft the Batman film, offered no other details outside of Manganiello stepping into the role such as when The Dark Knight's next adventure will hit screens or if Deathstroke is set to make a cameo in Justice League which is currently filming in London.
Affleck set to direct the Batman project, teased Deathstroke's appearance in Warner Bros. DC Extended Universe recently on social media by posting a video featuring the high-skilled assassin for hire staring menacingly at the camera as he sported his signature blue and orange armor.
Deathstroke, aka Slade Wilson, and also nicknamed The Terminator, was created by Marv Wolfman and George Perez in 1980. Known for taking on the Teen Titans and hunting down heroes for the right price, Deathstroke possesses incredible strength, reflexes, a brilliant tactical mind and the ability to regenerate.
The fan-favorite character has appeared in numerous comics, animated shows like Cartoon Network's hit Teen Titans series, video games and most recently was portrayed by actor Manu Bennett on Arrow.