Reports have previously suggested that the 26-year-old defender could have been sold by the Reds this summer.
Comolli told Liverpool’s official website: “We are absolutely delighted. We were in talks for a few weeks, but it was easy to find an agreement because he wanted to stay and we wanted him to stay.
“We are very pleased he wants to commit long term, and I think he was pleased we went to him and asked him to commit long term.
“His best years are to come. Very often defenders peak between 26 and 31, so he is just entering into those years where a maturity comes in and his knowledge of the game gets better and better. We are happy his long-term future is at Liverpool.”
Comolli added: “It’s obvious when you watch him play his technical ability is second to none. Physically he is absolutely fantastic as well and his fitness level is great.
“Towards the end of last season he showed how versatile he is by playing at left-back or right-back – mostly at left-back – and was outstanding.
“For us he is a great asset to have around. As we’ve always said, we don’t want to sell our best players or sell our assets and as long as the players are happy to be here, we’re happy to commit to them.”
