The 24-year-old has established himself as an integral part of the Sarries team since making his debut in 2014, helping the club to back-to-back Champions Cup successes in 2016 and 2017, as well as three Premiership triumphs in the last four years.
Itoje, who made his 100th appearances for Saracens in November, has also enjoyed success on the international stage, winning 26 caps for England to date, while he featured in all three Tests for the British and Irish Lions during their tour of New Zealand in 2017.
The versatile forward will be hoping to continue his development with both club and country over the coming years and he admits he is delighted to have extended his stay with Saracens - with his new contract set to run until the summer of 2022.
"I'm really pleased to be staying on at Saracens," Itoje was quoted as saying by the Saracens website.
"I've been at the club for 10 years now so I am really excited to see what the future holds for this great team."
Sarries director of rugby Mark McCall was equally delighted to see Itoje commit his future to the club.
"At Saracens, we take pride in developing players from within," McCall added. "Maro is an exceptional young man, on and off the field and it's been a privilege seeing him develop. We are thrilled he is staying with us."