The 'From Time' rapper, who is reportedly dating the 'Unapologetic' singer, has splashed out on the yellow diamond, although it is not believed to be an engagement ring.
A source told The Daily Star newspaper: ''Rihanna was delighted with the gift.
''She has accepted it as a token of Drake's love. He's now even changing his schedule to spend as much time as possible with her.
''It's all getting increasingly serious between them.''
The 'Stay' hitmaker, 26, and the 27-year-old star have been ''inseparable'' in recent weeks and Rihanna hopes he will ask her to start looking at properties soon so they can plan to move in together.
The loved-up pair have been dating exclusively for a number of weeks, following a brief fling in 2009, after Rihanna's split from ex-boyfriend Chris Brown.
The pair were photographed holding hands in London and embraced after Drake's performance at the MTV Movie Awards on Sunday night (13.04.14).
A source said: ''Rihanna immediately ran to Drake, jumped into his arms and planted a fat kiss on his lips.''