Allegri says the Portugal superstar had a private conversation with him on Thursday regarding his future and Ronaldo has already made his decision.
Ronaldo is said to be on the verge of returning to the Premier League to feature for Manchester United’s local rivals Manchester City.
Allegri was speaking at a press conference ahead of Juventus’ Serie A game against Empoli on Saturday and the Italian coach made it known about Ronaldo’s imminent exit.
"Yesterday Cristiano [Ronaldo] told me that he no longer has any intention to play for Juventus. For this reason, he will not be called up for tomorrow's game."
The former AC Milan coach added: "Cristiano is to be thanked for what he has done, also as an example amongst the youngsters.
"But as I said, we must go on.
"Things change, it's a law of life. Juventus remains, which is the most important thing. Cristiano gave his contribution, he made himself available, now he leaves and life goes on."
Ronaldo joined Juventus in the summer of 2018 after a successful nine-year adventure in Spain with Real Madrid.
He has scored 101 goals and provided 22 assists in 134 games in all competitions during his three-year stay in Turin.