The two apparently swapped numbers while out clubbing at London's Mahiki after they after they both played 95.8 Capital FM's Summertime Ball in June.
The 21-year-old told Metro: "It’s true. I met her in a club. She is very nice and very tall. She gave me a dance, she’s really nice – we did swap numbers."
The Metro also reveals that Siva's bandmates have been teasing him - starting a rumour that after a hot night out, Siva and Rihanna saw in the morning together with a a sausage and bean melt from Greggs bakery!
But despite the Umbrella star's attentions, Siva is apparently not ready to settle down just yet, saying that he has his eye on "all of The Saturdays".