The 18-year-old midfielder penned an extension to his contract on Monday, which means he will remain at St Mary's until the summer of 2017.
Ward-Prowse has featured in seven Premier League fixtures for the Saints this season.
Manager Nigel Adkins said: "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'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."
Ward-Prowse added: "It was nice that we got the win on Saturday, and it's nice to put pen-to-paper. I can kick on from here.
"That's been my dream since I was a young kid, so to get to that stage is fantastic."