The 24-year-old Scotland international joined Arsenal for £25m from Celtic in the summer of 2019 and has so far made 62 appearances for the club.
Tierney has impressed in his time with the Gunners, helping them win the FA Cup in his first season and only injuries have prevented him from playing an even bigger role for Mikel Arteta’s side.
Tierney said in an interview on Arsenal's Facebook page: "It feels amazing. First, it was the manager who came to me and said, 'We want you to extend your deal'.
"I had a hard first season with injuries and COVID and stuff, but last season it really picked up for me and the club have been brilliant with me so I'm more than happy to extend it, delighted.
"The vision of the club and where it wants to go and the expectations of the club is where I want to be in football. There's no doubt about it, we're not where we want to be just now, but we're going in the right direction.
"The confidence the manager's given me... when I spoke to him after I signed this contract I said, 'Thank you so much'.
"He took me when my confidence was at my lowest for sure - 100 per cent the lowest my confidence has felt - after my injury, moving away from home. I was so low and he's picked me up, he helped me, him and his staff."
Tierney was part of the Scotland side that recently exited EURO 2020 at the group stage.
