The former AC Milan goalkeeper was the penalty shootout hero as Italy defeated England in the final of Euro 2020.
Cannavaro said: “Donnarumma is the real champion of this Azzurri side.
“I am surprised that, before the Euros, somebody thought he was an average goalkeeper. There's nothing average in Gigio, just think of the tranquillity he has at 22. He will be the best goalkeeper for the next 10-15 years.
“I am happy Giorgio Chiellini lifted the trophy.
“He was in the stands to watch the 2006 World Cup Final and I played with him too, I really respect Giorgio."