The 27-year-old Brazil defender has committed to the Gunners, having had two years left to run on his previous deal.
"I arrived here as a young player and after almost five years I'm so happy and I've learned a lot," Gabriel told Arsenal's official website.
"I'm so proud of myself, it's an amazing journey, and I'm so happy to continue it. I hope I win some trophies with this club, because I love this club and my family loves the club, too.
"Arsenal is an amazing club and I'm so proud to sign a new contract. I love this club, I love the supporters, my teammates, I love this stadium. I'm so proud and thank you for all the support. We continue together for the future."
Gabriel has been one of Arsenal's key players since joining the ranks in 2020, making 210 appearances and scoring 20 goals from central defence.
He made 42 appearances for Mikel Arteta last season, before surgery on a hamstring injury curtailed his campaign early in April.
Arsenal are also in talks to tie down more significant players to new contracts, including Gabriel's playing partner William Saliba, Bukayo Saka and academy graduates Myles Lewis-Skelly and Ethan Nwaneri.