The Where Have You Been star was due to headline the event on Thursday (5th July) but has pulled out after Clara 'Dolly' Braithwaite lost her battle with cancer over the weekend.
Rock In Rio organisers confirmed the news last night (2nd July), stating that they intend to replace RiRi, while also offering refunds to disappointed fans.
The statement also offered well-wishes to the grieving 24-year old and her family.
The Bajan babe took to Twitter to pay tribute to GranGran Dolly after hearing about her passing, posting a series of touching images of her on the social-networking site.
Rihanna wrote: "Goodbye #grangranDOLLY get your beauty rest until I see you."
Her ex-boyfriend Chris Brown and his mother Joyce Hawkins also paid homage to Dolly, with Breezy tweeting: "Praying for family and the lost loved one. She was like my grandmother. Love you GRAN GRAN! RIP"
The Umbrella hitmaker later performed at Sweden's Peace & Love music festival, with some concertgoers stating that RiRi appeared shaky on stage, with Dolly's death clearly affecting the singer.
RiRi is still set to headline this weekend's Wireless Festival in London's Hyde Park on Sunday (8th July) as planned.
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