The 22-year-old Irishman joined Liverpool’s youth set up in 2015 and has made nine appearances for the senior team to date, including five last season.
Kelleher will most likely battle it out with Adrian, who also signed a new contract recently, to be Alisson Becker’s understudy next season.
After agreeing fresh terms in recognition of his progress, Kelleher told Liverpool's official website: "I am happy to get it over the line and finally done; it was in the pipeline for a few months with negotiations and stuff, so I am delighted to get it done.
"For me, it was a positive moment to commit my future to the club for the next few years. It's such a big club and it's an honour to be a part of it, so when I got the chance to sign for a few more years I was obviously delighted. I just want to keep my progress going at the club, really."
"It was a big year for me in terms of playing the first-team games this year and more important games; being thrown into the Champions League and Premier League games was big for my development and being able to handle that," Kelleher added.
"It gave me a lot of confidence to try to push on, to try to keep pushing Ali because I can play at that kind of level as well and do well."
Earlier this month, Kelleher made his debut for the Ireland national team in a friendly against Hungary.
