The 28-year-old, who was voted the 2017/18 Fans’ and Players’ Player of the Season, today finalised the deal, which runs until the summer of 2022.



McCarthy, who moved to St Mary’s from Crystal Palace in 2016, was an influential figure last term, as he broke into the team during the second half of the campaign.



In his 18 Premier League appearances, he kept seven clean sheets and made a series of crucial saves that helped secure a number of vital results, particularly in the closing weeks of the season.



Speaking after putting pen to paper, McCarthy said: “I’m massively pleased. I had one year left on my current deal and obviously I’m over the moon to sign a new four-year deal.



“I think the club is going in the right direction. With the way we finished the season, we can take that into this one and hopefully finish a lot higher up the table.



“Everyone is ready to go.”

Southampton manager Mark Hughes said: “Alex played a key role for us last season, and we are delighted he has agreed a new deal here.



“His performances last season speak for themselves, and it is clear how highly regarded he is by his teammates and also the supporters.



“It was clearly a priority this summer to ensure the commitment between him and the club was strengthened, and we believe Alex is very much in the right place to continue to grow and improve his game.”