The disaster occurred at Mount Meron at the main celebrations of Lag BaOmer, a holiday when tens of thousands of people, mostly ultra-Orthodox Jews, gather to honour Rabbi Shimon Bar Yochai, a 2nd century sage and mystic who is buried there.
Zaki Heller, spokesman for Israeli rescue service Magen David Adom, added about 150 people were hospitalised in the stampede.
Prime Minister Benjamin Netanyahu called it a “great tragedy” and said everyone was praying for the victims.
The incident happened after midnight on Friday, and the cause of the stampede was not immediately clear. Videos circulating on social media showed large numbers of people packed together in tight spaces.
A 24-year-old witness, identified only by his first name Dvir, told the Army Radio station that “masses of people were pushed into the same corner and a vortex was created”.
He said a first row of people fell down, and then a second row, where he was standing, also began to fall down from the pressure of the stampede.
“I felt like I was about to die,” he said.
Magen David Adom tweeted that it was treating 103 people, including 38 in critical condition. Israeli media had earlier reported that a grandstand collapsed, but the rescue service said all the injuries happened in a stampede.
The Israeli military said it had dispatched medics and search and rescue teams along with helicopters to assist with a “mass casualty incident” in the area.
It was the first huge religious gathering to be held legally since Israel lifted nearly all restrictions related to the coronavirus pandemic.
Large crowds traditionally light bonfires as part of the celebrations.
The country has seen cases plummet since launching one of the world’s most successful vaccination campaigns late last year.