Mikey, 25, triumphed over Demi, 62, Fernanda Torres, Karla Sofia Gascon, and Cynthia Erivo, to win the coveted gong for her starring performance in Anora.
Gascón had found herself in the crosshairs of controversy shortly after making history as the first openly-transgender actress nominated in the Best Actress category.
Demi's, 62, fury was palpable as the 25-year-old rising star's name was called out toward the end of the 97th Academy Awards - which featured a star-studded red carpet - in Hollywood on Sunday.
Cynthia spoke about the exact moment she found out she was nominated for the award for Best Actress at the upcoming Oscars ceremony at the Sundance Film Festival on Friday.
Megyn Kelly went on an explosive rant against Karla Sofia Gascon, the 52-year-old transgender star of Emilia Perez, after she was nominated for the Oscars' Best Actress award.
The 38-year-old Wicked star is hoping to take home the gong for Best Actress in a Leading Role, for her showstopping portrayal of Elphaba - the Wicked Witch of the West.