Things are getting serious (again) between on-again, off-again lovebirds Rihanna and Drake.

The pop stars are "officially exclusive," recently going from casual hook-up buddies to boyfriend and girlfriend, TMZ.com reported.

"They've decided to give it a serious shot," according to TMZ.

The 26-year-old starlet and the 27-year-old rapper have been spotted looking cozy in Europe as of late during Drake's tour there. The two reportedly have been inseperable, with RiRi spending every night with her man since she arrived overseas.

"He's in the best mood he's been in a long time," a source said.