Rihanna
Spends the Day
with Rob Kardashian
8/26/2012 4:30 AM PDT
Rihanna -- Spends the Day with Rob Kardashian
Rihanna and
Rob Kardashian spent their entire Saturday together ... going go-karting during the day (
above) and hitting up Playhouse in Hollywood at night (
below).

It's interesting ... the two were rumored to have hooked up all the way back in February, but nothing has been mentioned about the would-be pair since.
Rob is dating singer
Rita Ora and the two recently got each other's names tattooed on their hands.