What was Beyoncé's stage alter ego called during the late 2000s?

Beyoncé called her late-2000s stage alter ego Sasha Fierce.

She described Sasha Fierce as a more assertive, sensual, and fearless performance persona that appeared when she was onstage. Beyoncé contrasted that character with her private self, explaining that the alter ego helped her separate everyday life from the intensity of performing.

The name became central to the title of her 2008 double album, I Am... Sasha Fierce. The two-disc concept contrasted intimate songs on the “I Am...” disc with more energetic and performance-focused material on the “Sasha Fierce” disc.

Hits associated with the project include “If I Were a Boy,” “Single Ladies (Put a Ring on It),” and “Halo.” Beyoncé later said she had moved beyond needing the alter ego, but Sasha Fierce remains one of the clearest examples of a pop performer formalizing a stage persona.