Neither singer would confirm that they had rekindled their romance when asked in recent interviews, given his 2009 conviction for assaulting her.
However, the Umbrella star -- who's performing at the Aviva next June -- appeared to give everyone the proof they needed over the weekend after posting a picture of him on her Twitter page.
The snap, taken in Berlin, showed him topless and lying over a hotel bed with his jeans pulled down. Given that the Beautiful People star is surrounded by Simpsons memorabilia, Rihanna captioned it 'Bart Obsessed', sending the rumour mill into overdrive.
Now tongues are wagging about whether she'll join him at his Irish concert at Dublin's O2 on December 3.
Clearly not deterred by his bad-boy behaviour, she has been spotted in his company countless times over the past number of months.