Stefani will be temporarily replacing original coach Christina Aguilera, who had been expected to return to The Voiceafter Shakira filled in for her for Season 6, which is currently airing.
Aguilera, however, is newly engaged and currently expecting a baby girl with fiance Matthew Rutler. She will return to the show and sit in one of the four big red chairs for Season 8.
Stefani and Williams -- a Grammy Award winning singer and Academy Award nominee -- will take the stage during The Voice's Monday, May 5 broadcast on NBC. Stefani will sing "Hollaback Girl" from her debut solo album, "Love. Angel. Music. Baby." Williams is set to perform his new single "Come Get It Bae" from his current album "Girl."