In addition to Keyes' casting as Timberlake -- and Natasha Bassett's previously announced casting as Spears -- the network has also confirmed a few other famous roles.
Clayton Chitty has won the honor of playing Spears' other famous ex (and father of her two children) Kevin Federline, and Kelly McCabe has been cast as her childhood friend and husband of 55 hours, Jason Alexander. In addition, Peter Benson will play Spears' manager Larry Rudolph; Markian Tarasuik will play Wade Robson, her former backup dancer; and Nicole Oliver and Matthew Harrison will take on the roles of Spears' parents, Lynn and Jamie Spears, respectively.
Last but not least, Tamara Thorsen has been cast as Jenna Dewan-Tatum, who was a back-up dancer for *NSYNC during Timberlake and Spears' romance.
Britney -- which will follow Spears' rise to stardom, public breakdown, and return to the spotlight -- is set to air on Lifetime in 2017.
The pop star, however, has no part in the making of the movie. "Britney Spears will not be contributing in any way, shape or form to the Lifetime biopic, nor does it have her blessing," Spears' rep told ET last month, when the Lifetime movie was announced.