The highly rated 18-year-old midfielder, the latest young talent off the production line at St Mary's Stadium, ties himself to the newly promoted side until 2017
After being promoted into the first team at the beginning of the season and starting the Saints' first game against Manchester City, the 18-year-old has been on manager Nigel Adkins' teamsheet for each Premier League fixture since.
And, after a morale-boosting 3-1 win over fellow strugglers QPR, Ward-Prowse told the club's official website: "I'm absolutely delighted.
"It was nice that we go the win on Saturday and it's nice to put pen to paper. I can kick on from here.
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Adkins praised his 18-year-old prodigy, adding: "As one of the youngsters coming through the system, James has done ever so well since he stepped up to the first team during pre-season.
"He started the first game of the season and played there on merit; he works hard in training.
"He's a great lad in respect of being a role model for the younger players and he works very hard at his game every single day.
"We're delighted that we've got a hungry and ambitious young man who has now committed his longer-term future to the football club."