The goalkeeper’s previous deal was due to expire at the end of the 2013-14 season, but he has now committed himself for the following two campaigns as well.
Having arrived at St Mary’s in the summer of 2006, Davis’s new contract will extend his affiliation with the Club to a decade and take him through to his testimonial year.
The 36-year-old is Southampton’s current longest-serving player with 283 appearances under his belt, which represents an average of over 40 appearances per season since he joined from Sunderland six-and-a-half years ago.
During that time Davis has seen Saints placed into administration and relegated into the third tier in 2009 before Nicola Cortese led the takeover of the Club that summer.
Since then, the goalkeeper has been heavily involved as Saints won the Johnstone’s Paint Trophy in 2010 before back-to-back promotions led the Club to the Barclays Premier League last year.
There were personal honours for Davis too, with the stopper taking his place in the PFA League 1 Team of the Year in 2009-10 and 2010-11, as well as the Championship Team of the Year last season.
Competition from Artur Boruc and Paulo Gazzaniga has limited the stopper to nine appearances this season, though he has played a vital part in the team’s progress through his role as Club Captain.
Stalwart Davis is well respected by the board and management staff and much-loved by his fellow players and the Club’s supporters, therefore his decision to prolong his stay will undoubtedly be seen as a welcome one.
"When I first came to this club, to say that I would have been here for this period of time is something that I would have dreamed about," said Davis.
"For that dream to have materialised and for me to be feeling good is something I am really, really pleased with.
"I've seen a few things – a few ups and downs – but since Nicola Cortese arrived with Markus Liebherr, the Club has been on a journey.
"Little did I know the success, the drive and the constant improvements that would come once they got their teeth into the job," he added.
"If those guys hadn't been here then I certainly wouldn't have been either, and it's great that I've been a part of that under Nicola's leadership. That has allowed me to fulfil my dream.
"I don't think anyone connected with the Club can doubt what has been achieved here.
"Nicola in particular has been a massive part of my situation and me being at this club. He's made promises in the past and, from my point of view, he has delivered even more than he promised in the outset.
"He's the sort of guy who believes that achievements are to be rewarded, and he's certainly proved that with myself."
First Team Manager Mauricio Pochettino commented: “As Club Captain, Kelvin plays an extremely important role at Southampton.
"His presence in the dressing room is second to none, and his experience has proved to be vitally important to the Club as we look to achieve our aims.
"He has been a massive part of this club during his six-and-a-half years here, and there are few things in football that he hasn’t seen so far in his career.
"Every successful team needs to have characters and people like Kelvin, so I’m delighted that he has committed himself to the Club for a further three-and-a-half years."