The 26-year-old has made 177 appearances for the Aviva Premiership outfit since making his debut in 2009, while he has 17 international caps for England and also appeared in all three Tests for the British & Irish Lions in New Zealand this past summer.
On signing the contract, George said on the club's website: "It's the club that I've grown up playing for, the club I've grown up supporting my whole life. To be signing here for the long-term and to have played here for a long time already is a huge honour."
Saracens director of rugby Mark McCall added: "We're over the moon to secure Jamie's long-term future. He is fast becoming a world class player in his position, and is a key figure for both club and country.
"Jamie is a real example for our younger players to follow. It's well documented how patient he had to be earlier on in his career and both Jamie and Saracens have reaped the rewards from that.
"He is another player who has progressed through the ranks at Saracens to become a key player for club and country. He is a Saracen through and through, and his hunger and drive to keep on improving is exceptional."
Meanwhile, Saracens have also tied down 19-year-old lock Nick Isiekwe and 20-year-old Max Malins to new two-year contracts at Allianz Park.
McCall added: "In Nick and Max, we have two players who are showing huge promise and have a number of senior appearances under their belts already."