He told manutd.com: "I think he's been the biggest influence in my career. He's watched me play since I was 13 so it's been over 20 years.
"I watch him closely- the hunger and desire to keep improving and not just settle for a couple of trophies. Each season he takes up the challenge and wants to win more."
Sir Alex has a fearsome reputation but Giggs revealed that the famous hairdryer treatment appears less frequently these days.
"He's a lot more relaxed and calm now," Ryan added. "When I first came to the club as a 13-year-old I'd never seen anything like it- the team talks.
"Even with the youth team he would have a go at us at half-time. But I think he enjoys watching this team play and watching this team develop."
And with a third Champions League final appearance imminent, Giggs admitted his desire to win the trophy remains as strong as it was back in 1999. "Winning the Champions League was such a great achievement but when you've tasted it you want to do it again, to get that feeling again."