The 30-year-old Republic of Ireland international is the club's reigning player of the season and is nearing full fitness following the knee injury which kept him out of the final few games of the 2015/16 campaign.
And as his return to action moves closer, he has agreed to commit his future to the Magpies until at least 2020.
Elliot, who joined Newcastle from Charlton five years ago, said: "I'm delighted. Personally, I had a good run in the team last year but I was obviously gutted at the end with the injury so it's a real confidence-booster that the club have put their faith in me.
"It's helped my rehab as well, because it's something to work towards, and it ties everything up perfectly now so I can look forward to the future, commit to getting back fit and hopefully getting us back to where we want to be."
Manager Rafael Benitez added: "I'm really pleased that Rob has signed a new contract with the club.
"It shows our confidence in him as a goalkeeper for now and for the future. Hopefully he will be challenging for the goalkeeper position again very soon."