The 32-year-old former Celtic goalkeeper has signed a deal to until the end of the season with Nigel Adkins side, having been without a club since his release from Fiorentina at the end of last season.
He had been training with Everton after a move to QPR fell through at the last moment, but it is newly promoted Southampton who have sealed the deal.
Speaking after signing a contract, Boruc expressed his relief at finally signing for a Premier League club.
“I’m looking forward to playing in the best league in the world while I’m playing here at Southampton. I’ve finally found the club I was looking for,” Boruc told Southampton’s official website.
“My dreams are coming true. I’ve been talking about this for a long time, and finally I’m here in the Premier League.”
Adkins may be tempted to throw Boruc straight into the first team, with first choice keeper Kelvin Davis looking somewhat uneasy during the opening five matches.
However Adkins was keen to stress the importance of competition for places within his squad.
“He now gives us a third goalkeeper in the building, which is important because the potential for injuries and people getting sent off means we have to cover ourselves,” said Adkins.
‘He gives us back-up and competition,’ he added.
Boruc could be in line for his debut when Southampton travel to Goodison Park to take on Everton this Saturday.