What name did Beyoncé give her onstage alter ego introduced around 2008?

Beyoncé named her onstage alter ego Sasha Fierce.

She described Sasha Fierce as a more performance-focused persona that appeared when she was onstage. The name became especially prominent with the 2008 album I Am... Sasha Fierce, which presented contrasting sides of her artistic identity.

The album was structured around two discs: I Am... emphasized more personal ballads, while Sasha Fierce focused more heavily on energetic pop and R&B performances. Songs associated with the project include “If I Were a Boy,” “Single Ladies (Put a Ring on It),” and “Halo.”

Beyoncé later said she had retired the Sasha Fierce persona because she no longer needed to separate her public performance identity from her own personality. “Yoncé” is a different nickname used in later music and performances.