The 29-year-old was part of the Aussie side that lifted the Webb Ellis trophy in 1999 and his record also includes two Super 12 titles with the ACT Brumbies.
He will compete with Andy Titterrell, Olivier Azam and Ross McMillan for the hooking duties.
Ryan said: "This is a major signing for Gloucester Rugby and I'm delighted that Jeremy will be running out at Kingsholm next season.
"He will add tremendously to the talent at our disposal, but more importantly as someone with more than 70 international caps he will bring huge experience and leadership qualities to the side.
"We're building a squad capable of consistently challenging for the major domestic and European honours and Jeremy is a key part of the jigsaw."
Paul, who was born in New Zealand but moved to Brisbane as a teenager, decided to join to Gloucester after being won over during a visit to Kingsholm earlier this season.
He said: "I still have some ambitions to fulfil in the international game before I depart but this is a new chapter in my life.
"I had the opportunity to visit Kingsholm to watch a match and it certainly lived up to its reputation.
"I met with Dean Ryan and the coaching staff and we share a lot of common beliefs about how the game should be played."