The goalkeeper put pen to paper on the deal following the conclusion of the 2020-21 season to commit his future to the Reds following a watershed campaign, in which he made five first-team appearances and featured in both the Premier League and Champions League.
The 22-year-old also won his first cap for Republic of Ireland earlier this month, coming on as a second-half substitute against Hungary in Budapest.
Speaking about the new contract, Kelleher told Liverpoolfc.com: “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.