Image of Lennox Lewis Lennox Lewis Former world heavyweight champion and BBC pundit
"Anthony showed heart and went big. When the going gets tough, the tough get going. When he decides to turn pro, he will be a great pro. He has the size to be the next world champion."
Joshua, 22, was unlucky to be trailing by three points going into the final round against the defending champion.
But needing a grandstand finish, Joshua came on strong down the stretch.
The judges scored the fight 18-18 with Joshua winning on countback. The Italians appealed against the decision but were ultimately unsuccessful.
"There are no easy fights in these Olympics," said the Briton. "I have pulled it out of the bag and my heart is pumping with adrenaline.
"The third round is always a good round for me. Again and again, the crowd have come out."
He added: "That medal represents my journey and the support from my team. It is much more than a gold medal, it is a life experience."
Joshua's display puts a golden cap on Britain's best performance in an Olympic boxing tournament since 1920. Britain won six medals at the Antwerp Games but only two of them were gold.