What alter ego did Beyoncé use for her 2008 double album?

Beyoncé used the alter ego Sasha Fierce for her 2008 double album.

I Am... Sasha Fierce was released on November 12, 2008. Its two discs presented contrasting sides of the performer: the I Am... disc emphasized more personal ballads, while the Sasha Fierce disc focused on more assertive, dance-oriented material.

Beyoncé described Sasha Fierce as a stage persona that allowed her to perform with heightened confidence and energy. The concept became closely associated with songs such as “Single Ladies (Put a Ring on It)” and “Diva.” The album was commercially successful and produced several major international hits.

Beyoncé later said she had retired the Sasha Fierce persona because she felt she no longer needed an alter ego to access that confidence. The name is therefore specific to a period of her career, rather than her permanent professional name or a separate recording artist.