"There is a great set-up and everyone is determined to make a serious attempt at winning promotion this season.
"The club has been in League One long enough now and we need to get back to challenging for a place in the Premiership.
"I'm really looking forward to getting started and hopefully challenging for a first-team place."
The 26-year-old former Brentford man joined Southampton in 2004 and made 22 appearances for the South Coast club.