Rabbi Eli Schlanger has been confirmed as one of the victims of the Bondi Beach terror attack.
His first cousin, Rabbi Zalman Lewis, announced his death in a post online.
"My dear cousin, Rabbi Eli Schlanger, was murdered in today's terrorist attack in Sydney," he wrote.
"He leaves behind his wife and young children, as well as my uncle and aunt and siblings.
"He was truly an incredible guy."
The deadly attack unfolded on Sunday afternoon as hundreds gathered at the world-famous Bondi Beach to attend the "Chanukah by the Sea" event, making the first day of Hanukkah.
Sixteen people were killed, including one of the gunmen, and a further 38 were taken to hospital.
Following the attack, Israel's foreign ministry said one of its citizens had been killed and another had been injured.
It is not clear whether the Israeli foreign ministry was referring to Rabbi Schlanger.
'Devoted rabbi'
Rabbi Schlanger was the head of the Chabad mission in Bondi.
He had served as a rabbi and chaplain in the community for 18 years, Chabad said.
He was one of the organisers of the event that was targeted by the two gunmen on Sunday evening.
Rabbi Schlanger told Chabad.org earlier this year that the local Jewish community had tightened security in the wake of a surge in antisemitic incidents.
He highlighted Chanukah by the Sea in particular for doubling its attendance over the past few years.
Chabad.org described him as "a devoted rabbi and chaplain, working tirelessly … to support Jewish life in the Bondi community".
