The Toon defender, 23, has signed fresh terms to keep him at St James' Park until 2023.
Lascelles said: “I'm over the moon. I love the city, the football and the fans.
“Everything about it, I enjoy so I'm happy to be tied down for the next six years here.
“We've got a group of ambitious lads, the fans are excellent and the manager has got trust in me, so I'm really happy here and I want to take the club as high as it can go."
Boss Rafa Benitez added: “As soon as I made the decision to make Jamaal the captain of Newcastle, he rose to the challenge and he has developed as a player and a character.
“He has proven himself to be a very good leader and a good role model too.
“He has also improved as a player, responding well to our advice and guidance and getting better with every game."