The former Super Rugby player faced his new employers twice this season in the Pool stage of the Heineken Cup and made his International debut for the pacific island against Ireland at Lansdowne Road in 2001.
"I'm excited about signing for the Ospreys and what looks like an exciting challenge ahead," said Stowers.
"I've spoken at length to the coaches about their vision for the team, had a good look around the first class facilities there, and I'm really looking forward to being able to play a part in what they are trying to achieve.
"I've played against the Ospreys twice this season so I know a bit about the squad there, and from what I've seen of them over the last few months in the LV= Cup and the Magners League, there's strength in depth with some really good youngsters coming through that I can help develop.
"It's a fantastic opportunity for me to be part of a forward thinking and ambitious set-up, and it's an exciting move for me, personally and professionally, that will allow me to experience rugby in new environments."
Elite Performance Director, Andrew Hore, said:
"George will bring a real physical presence to our back-row, and as we experienced ourselves in the two games against
London Irish in the Heineken Cup, he provides a real nuisance value, making life incredibly difficult for the opposition with his high work-rate.
"He is also a proven leader with experience of captaincy at international level, and we've no doubt that he will prove to be a real asset to the Ospreys over the next two years. As a player who has made a huge impact in England during the last two seasons, we are extremely pleased to have secured his services and we look forward to welcoming him to Ospreylia."