British pop singer Rita Ora -- who had the hit song, "R.I.P." -- collapsed on the set of her photo shoot in Miami Beach today ... and was rushed to a hospital by ambulance according to photographers on the scene. Photos show the 22-year old singer/model/actress -- eyes closed -- being unloaded from the ambulance on a stretcher ... attended by emergency personnel. So far, no word on what may have caused her to collapse. Ora -- who famously dated Rob Kardashian last year -- was reportedly preparing for her photo shoot on the beach near the SoHo Beach House hotel when she fainted in her makeup trailer. We've reached out to Rita's people -- so far, no word back.