"Let's clarify this issue, Ronaldo told me that he's staying," Allegri said in response to numerous questions on Ronaldo's form and mindset.
"He has always trained well and has always been available. I've read rumours in the papers, but he's never wanted to leave Juventus."
Italy's top scorer last season with 29 goals was absent for Juve's final warm-up against the club's youngsters on Thursday, but Allegri said he was ready to play in what will be his fourth and final season of his contract.
Allegri's comments follow the 36-year-old's own rejection of reports he was angling for a return to Madrid under Carlo Ancelotti, calling such talk "disrespectful".
In an Instagram post this week Ronaldo said his "story at Real Madrid has been written", although he did not explicitly say that he was not looking for a way out of Juve.