The goalkeeper, 32, has extended his deal to 2025.
Gillespie said: "I'm delighted to be extending my contract into next season. This is the club I grew up supporting and it's a hugely exciting time to be a part of it.
Advertisement
Advertisement
"We have a brilliant group in the dressing room and at the training ground, and it's a great environment to work in. I'm already looking forward to pre-season and to getting back onto the grass."
Newcastle United manager Eddie Howe said: "Mark's attitude to his work and his consistency are of the highest order.
"He continues to set an example in how he trains, plays and supports his teammates, and that's a hugely important component in any squad. I'm delighted to have him with us."