got hot under the sun at Coachella this weekend -- where she was looking hot as well!

The sexy singer was one of many stars in the desert for the annual music festival, where she not only went to other people's shows, but performed too.

Before hitting the stage with Calvin Harris on Sunday night, Rihanna soaked up the sun in a denim bikini ... and shared photos with her fans on Twitter.

RiRi has a history with posting bikini pics online -- check out her hottest swimsuit shots above!

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