An estimated 15,000 people watched Rihanna count down to the switch-on moment, which was followed with a firework and laser display.
Rihanna then performed her single ‘Diamonds’ from her new album, which launched in the UK yesterday.
Myf Ryan, general manager of UK marketing at Westfield, said: "Christmas is always such a special time of year for Westfield and we are so excited that Rihanna has chosen Westfield Stratford City to help celebrate the festivities. Our shoppers love Rihanna and we are proud to be able to host this unique and exclusive concert for the UK fans."
Rihanna was joined on stage by young ambassadors from Save the Children, Westfield’s Christmas charity partner.
The east London shopping centre is no stranger to high-profile celebrity appearances – last year Justin Bieber turned on the lights.
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