There had been rumours previously, but now it's official, Charlize Theron will play the villain in Fast 8

There's no word yet on who she'll be actually playing but there had been speculation that she'll be yet another member of the nasty Shaw family (previous siblings include Luke Evan's Owen and Jason Statham's Deckard) who've been causing Vin Diesel and co nothing but grief since Fast and Furious 6. 

Though it's most likely she'll be unrelated (how man powerful criminals can one family have right?) and will be new foe. She'll be joining returning cast members Vin Diesel, Dwayne Johnson, Jason Statham, Michelle Rodriguez and Tyrese Gibson. 

F Gary Gray, fresh off the success of Straight Outta Compton will be taking over directing duties from James Wan. 

Via Empire