Lee, 28, previously played for the club in the English Premier League back in 2008/09, and has spent the last decade with the Panthers.
He said: “I am very excited to be returning to Guildford. It’s a great organisation to be part of, with a great fan-base. I had an amazing time there 10 years ago.
“I have nothing but great memories from my first stint with the club and hope to make many more.
“The Flames had a great season last year and it’s a great sign to see a large portion of that team already signed up.
“Hopefully I can help the team add to the success they earned last season. I can’t wait to meet the guys and get started.”
Lee has made just shy of 700 games in his career, winning six Challenge Cups, a league title and four play-off titles.
Internationally, he has won 49 caps for GB and was part of the recent World Championship campaign.
Flames head coach Paul Dixon said: “It is a pretty big signing for us to be able to get a GB player of his level into our lineup,.
“He has obviously come a long way from when he was just getting started here as an 18-year-old, and he has become a very solid defensive guy back there which he demonstrated while playing against the world’s very best players this past Spring.
“We know that he was really excited about possibly returning here and we are thrilled to not only get a player of his quality, but also a character guy with personality and leadership attributes that are great additions to our lineup.”