The 33-year-old Poland international's contract had been due to expire at the end of this season but, having established himself as Southampton's first choice keeper in recent months, he has agreed to stay on.
Southampton are 12th in the table with 38 points from 33 games, seven points above the relegation zone.
"Artur deserves this contract because, in the three months that I've been here, he has been crucial for us," manager Mauricio Pochettino said on the club website.
"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."
Boruc's deal follows new contracts in recent months for captain Adam Lallana, striker Rickie Lambert, keeper Kelvin Davis and midfielders Morgan Schneiderlin and Jason Puncheon.