The 32-year-old has made over 100 appearances for the Cherry and Whites since his move from West Country rivals Bath in 2005 and has captained the side this season.
The 2003 World Cup winner will win his 70th International cap against Scotland this weekend and is delighted with the new deal.
"I didn't really entertain the idea of being anywhere else to be honest. I love the club, the supporters, the area. Signing on again wasn't a difficult decision," he said.
"Bryan and the other coaches have created a great atmosphere around the club and we're all enjoying our rugby."
"This season has been good but we still have some massive games to come which will determine exactly how good it will have been once it's all over. I'm looking forward to playing my part."
Head Coach Bryan Redpath admitted he was delighted to secure the services of his skipper:
"Tins has been a huge part of what we've achieved to date and will be a big part of what's to come."
"He's an influential figure on and off the pitch and having him on board is a big bonus for us