Williams, best known as a member of the R&B group Destiny's Child, which has sold 35 million albums worldwide, will replace Toni Braxton, who has been with the show since late June.
This will be Williams' Broadway debut.
The Disney musical by Elton John and Tim Rice has done very well with Braxton. Most weeks of her run have topped $700,000, a good six figures above what the production had been averaging in previous months.
"Aida" opened March 23, 2000.