The Scotland international is yet to appear for Liverpool this season as he looks to recover from an ankle injury he sustained during preseason.
Robertson is the latest Liverpool player to sign a new long-term extension, with goalkeeper Alisson Becker, defenders Virgil Van Dijk and Trent Alexander-Arnold and midfielder Fabinho all inking new deals in the past month.
"Obviously when the negotiations started and it looked as if my future was going to be here longer term than what it was, then I think it's no secret that I'm happy at this club," Robertson said in a statement.
"I want to stay at this club for as long as possible and to extend my stay, it's always a happy time for me, for my family. We're settled here, we love everything about this football club and I'm glad that the journey is continuing.
"When you sign for a massive club, I still remember the day as if it was yesterday when I signed here and obviously you have ambitions to become a regular player for Liverpool, to win trophies for this club, to do everything else but the way it's gone has been excellent."
Robertson, 27, has made 177 appearances since joining the club from Hull City 2017. He was a crucial part of the Liverpool side that ended the club's 30-year Premier League title drought, as well as being apart of its 2019 Champions League-winning side.