Mankiewicz was a reporter who entered into Hollywood and co-wrote 1941's Citizen Kane with the film's director Orson Welles.
Mankiewicz, who also worked on other classic films such as The Wizard of Oz and Gentlemen Prefer Blondes, accused Welles of trying to take sole credit for penning Citizen Kane.
Citizen Kane, considered to be one of the greatest films of all time, only won one Oscar for Best Original Screenplay. Mankiewicz and Welles were both awarded but did not attend the Oscar ceremony.
Fincher is directing based off a script by his late father Jack who wrote the screenplay prior to his death in 2003.
Mank will be presented in black and white with production set to begin in November. Fincher is producing alongside Cean Chaffin and Douglas Urbanski.
The biopic will be Fincher's first feature film work since helming 2014's Gone Girl. Oldman's last biopic role earned him the Oscar for Best Actor after he portrayed former British Prime Minister Winston Churchill in 2017's Darkest Hour.