ABC has confirmed speculation that the 'Only Girl (In The World)' singer will be the first performer to take to the stage at the November ceremony.
"We could not be more excited to officially announce one of pop music's biggest stars to open the celebration at the AMAs. Be sure to tune in so you don't miss this surely memorable moment," said the show's producer Larry Klein.
Rihanna, who has made three previous appearances at the AMAs, will join previously announced performers including Justin Bieber, Katy Perry, Ke$ha, Christina Aguilera, Pink, Bon Jovi, Diddy-Dirty Money, Ne-Yo and Usher at the event.
Eminem and Lady Antebellum will enter the evening with the most nominations - each at five - while Bieber has scooped four nominations and Ke$ha, Perry, Usher and B.o.B have all been recognised in three categories.
The 38th annual American Music Awards airs live from the Nokia Theatre in Los Angeles on November 21 from 8pm ET on ABC.
> In Full: American Music Awards - Nominees