The 33-year-old's contract was set to expire at the end of this season, but the Poland international has agreed terms on an extension after establishing himself as the club's No. 1 keeper since manager Mauricio Pochettino's arrival in January.
"I am very pleased and I'm proud to be a part of a big prospect," Boruc told the club's official website. "As a club, I believe we can achieve a lot over the next two years, and I'm looking forward to that.
"As I've said before, [the Premier League] is probably the best place to play football, and nothing has changed my mind on that since I came to Southampton."
"The new manager has changed a lot - we're playing totally different football, and I think that football is quite nice to watch and quite effective.
"Playing this style of football you can achieve a lot, and you need to be ambitious in your life. We've been getting points against teams like Liverpool and Manchester City, but I think we can get even better. We're looking forward to the next game."
Pochettino says the new deal is just reward for Boruc's competitiveness and bravery.
"I'm very happy and very satisfied," Pochettino said. "Artur deserves this contract because, in the three months that I've been here, he has been crucial for us.
"He has a very strong personality and character. He is very brave in the way that he plays and, with our brand of football, it's very important that we have a keeper like Boruc for the long term.
"It's especially important for him to go into the last few games of the season with the confidence of the club and to know that he's going to be here for the next two years, because that suits his competitiveness."
The move likley limits the first-team opportunities with the Saints available in the coming seasons for U.S. Under-20 goalkeeper Cody Cropper, who has been playing for the club's U-21 side in his first season with Southampton.