The 'ChiP Diddy Chip' hitmaker - whose real name is Jahmaal Noel Fyffe - met the "real hottie" singer in a club and helped her avoid a crowd because he is a "gentleman" - and was thrilled when she knew who he was.
He said: "Rihanna is a real hottie. I bumped into her in a club when she was having difficulty getting to the toilet because of all the people there.
"So I was a gentleman and helped her get past, not because it was Rihanna, but because I like to have good manners.
"As she went by, she looked up and said, 'Chipmunk!' It was pretty cool that she knew me and she was proper nice. I like the long, red hair, though she's even better with it short."
Earlier this year, the 20-year-old rapper praised Rihanna's ex-boyfriend Chris Brown - who was convicted of assaulting the singer in 2009 - for his work on their 'Champion'.
He said: "It's from the heart, it's a true story. I felt every single word and Chris meant every single word. I didn't want it to feel like I was just moaning about life. I wanted to uplift the people so I knew it needed something. It needed belting out.
"That's when I thought of Chris Brown. Nobody else is going to sing this better than him."