The 24-year-old centre-back had entered the final two years of his previous deal in North London, which had prompted a number of teams to scout the Frenchman, including Real Madrid who were eager to lure him away.
However, after establishing himself as a key part of manager Mikel Arteta's side, the club rushed to discuss a new deal which has been announced on Tuesday morning.
Saliba signed a new long term deal until 2029 and spoke on how proud he is to be staying with the side.
"I feel proud of myself because I first signed in 2019, and now in 2025, I'm still here to extend my contract. I'm so happy," Saliba told club media.
"I feel at home. We have a good team, we have a good squad, we have good staff. The coach is perfect for me, so it's the best place to be.
"I enjoy every day when I have the chance to wear this shirt. I try to give everything, and now I'll give even more to this club and to the fans."
Saliba signed for Arsenal in 2019 from Saint-Etienne and has since made 140 appearances for the Gunners under Arteta who says he is delighted with the new contract which secures the defender for years to come.
"William is loved by all the players and staff, and that speaks volumes about his character, commitment and attitude every day.
“Since joining us, William has grown so much, embraced responsibility, and has created a strong connection with our supporters and everyone at the club.
"We know there is still so much to come from him and will continue to work together to keep improving with the clear ambition of winning major trophies."