Ferguson, who helped Ronaldo develop over a six-year spell at Old Trafford after signing him as an 18-year-old in 2003, was at the Stade de France in Paris to witness Portugal earn a 1-0 win over the tournament hosts.
Ronaldo, who won nine trophies at United before joining Real Madrid in 2009, was happy to spot his former boss while making his way back onto the pitch after lifting the trophy with his teammates.
Ferguson waited to congratulate the team as they walked down the stadium steps with their winners' medals, and specifically picked out his former players Nani and Ronaldo for hugs.
Video: Heartwarming meeting between Sir Alex Ferguson & Cristiano Ronaldo after he wins Euro 2016 with Portugal. https://t.co/4CeRkN052D— Man Utd Stuff (@ManUtdStuff) July 11, 2016
A strike from substitute Eder in extra time won the final for Portugal, who were without captain and talisman Ronaldo from the 25th minute after he was stretchered off with a knee injury.
Portugal's triumph marks their first ever title win at a European Championships.