The Mexican actress will play clairvoyant Pina Auriemma in the drama, which chronicles the murder of fashion empire heir Maurizio Gucci.
"So happy to have my good buddy Salma join our wonderful cast!" producer Giannina Scott tells Deadline. "I've been talking with her about this Gucci project for 20 years! Now it's happening and she is a part of it."
Gaga leads the cast as Patrizia Reggiani, who was sentenced to 25 years behind bars in 1998 for plotting to kill her husband, Gucci, played by Driver.
Maurizio allegedly angered Patrizia, whom he shared two daughters with, after he left her for another woman.
While she was depicted as a hot blooded woman out for revenge and dubbed the Black Widow, her children blamed her actions on the aftereffect of the medical procedure where she had a brain tumour removed.
Giannina Scott reportedly has been eyeing the movie for a long time. The producer started to pursue the movie, framed around the rise of a family business that denigrated into squabbles over control of the business and greed, at a time when Gucci was being corporatised.
The script is penned by Roberto Bentivegna and is based on "The House of Gucci: A Sensational Story of Murder, Madness, Glamour, and Greed" by Sara Gay Forden.
The MGM movie is slated for release on November 24, 2021.