The 'Russian Roulette' singer - who was first linked to the baseball star at the beginning of the year - has finally confirmed she is dating the hunky sportsman but insists the pair are just having "fun".
She told Ryan Seacrest on his KIIS FM radio show: "He's my boyfriend.
"It's new, and it's fun, and it's nothing too serious, you know. I don't want anything that's going to take up so much of my energy and time right now in a bad way. I just want to have fun, and that's what it's about."
Although the 22-year-old beauty has no plans to settle down in the near future, the same cannot be said of her friends.
Katy Perry is set to tie the knot with fiance Russell Brand later this year and has given Rihanna the daunting task of organising her hen party.
The 'Umbrella' hitmaker said: "She put that on me last week. Now I have to come up with something cool, because she's getting married in India, so I'm like, okay now what do I do to match that for a bachelorette party?"
As well as giving Katy a party to remember, Rihanna is also focussing on her forthcoming 'Last Girl On Earth' tour - which starts in Seattle on July 2 - and has been taught to play the drums for it by blink-182 drummer Travis Barker.
She said: "It's so difficult. It's a lot of coordination. I thought I had coordination until I started playing drums. But he makes it really clear to understand."