Beyoncé's performance alter ego introduced during her 2008 era was Sasha Fierce.
The name became especially prominent with I Am... Sasha Fierce, Beyoncé's third studio album, released in 2008. The album was structured as two discs: “I Am...” emphasized more vulnerable and personal songs, while “Sasha Fierce” presented a bolder, more performance-driven side.
Beyoncé later explained that Sasha Fierce represented a stage persona she used while performing. The distinction helped frame the album's contrast between private emotion and public confidence, although she eventually said that the alter ego was no longer necessary because she had grown into the qualities it represented.
Sasha Fierce is not Beyoncé's legal name and is not the same as “Yoncé,” a nickname used in some of her music. The term is specifically associated with the 2008 album era and its performance concept.