The "Umbrella" star and the 18-year-old R'n'B singer were spotted getting hot and steamy at a Paris Fashion Week party for photographer Peter Beard last weekend.
A source told Us Weekly magazine: "Chris and Rihanna were aware of people watching them but couldn't keep their hands off each other. It was a very sexy public display of affection."
"By the end of the evening they were kissing passionately and Rihanna was lying in his arms. If people weren't sure they were going out before they certainly knew afterwards."
Rumors the pair are dating first surfaced last month when they were seen smooching at Rihanna's surprise 20th birthday party at Los Angeles nightclub Les Deux.
Just a week later, they were seen hugging in a swimming pool in Jamaica during a sun-drenched break.
However, Rihanna recently denied the pair are together, insisting: "Rumors come with the territory and you can't help these things."
"I'm single. If a good guy comes along we'll make it work, but for now I'm having fun being a single woman."
