Three years after arriving at Parkhead, the 30-year-old has agreed a deal that will take him through to the conclusion of season 2023-24.
Bain was recruited by Brendan Rodgers and played 74 times for Celtic, picking up three Scotland caps against San Marino, Kazakhstan and Mexico along the way.
Though currently playing back-up to Joe Hart, Bain has been number one choice during his time at the club – and he said it was a ‘privilege’ to be part of the Parkhead squad under Ange Postecoglou.
He told the club website: “I am delighted to agree this new contract extension. It is a privilege to be part of this great club and I am so pleased to extend my future at Celtic.
“We have already had success under the new manager, it is fantastic working with him and the rest of our backroom team, and I want to join them and the other players at the club in working hard to achieve more and more success for our fans.”
Bain last played against St Mirren on December 22 and is one of four goalkeepers at Celtic with first-team experience at the club, all vying for a position in Postecoglou’s team.
Joe Hart is the current preferred first-team starter, while Bain has been a regular understudy this season.
Academy graduate Conor Hazard who was the penalty hero in the delayed 2020 Scottish Cup final win over Hearts as is Vasilis Barkas, though there is speculation over the Greek international’s future at Parkhead.