He lamented that "we have yet to see a unified and resolute stance against the most anti-Semitic regime on the planet, a regime that openly seeks to develop nuclear weapons and annihilate the one and only Jewish state".
In a similar vein, US Vice President Mike Pence urged the international community to "stand strong" against Iran, calling it the sole country where Holocaust denial is "state policy".
Tehran denies it is trying to produce a nuclear bomb and rejects accusations of anti-Semitism, insisting that while it opposes the Jewish state and supports the Palestinian cause, it has no problem with Jewish people - including its own Jewish minority. Pence and other leaders from dozens of countries were at the Yad Vashem Holocaust memorial centre for the biggest international diplomatic gathering ever held in Israel, to remember the liberation of the Auschwitz death camp where the Nazis killed more than 1.1 million people, most of them Jews.
'Defend peace'
Russian President Vladimir Putin told the meeting that the victors of World War II, which became the five permanent UN Security Council members, "hold a special responsibility to save civilisation".
Putin, who has promoted Russia as a global powerbroker, proposed a 2020 summit of those countries' leaders to "defend peace" in the face of global instability. It was Russia's Red Army that liberated Auschwitz on January 27, 1945, but the Jerusalem gathering has aggravated a heated debate between Moscow and Warsaw over wartime history.
Poland's President Andrzej Duda stayed away after being denied an opportunity to address the event, organised by Moshe Kantor, a billionaire close to the Kremlin. Last month, Putin provoked an outcry by falsely claiming that Poland had colluded with Adolf Hitler. Poland sees Moscow as rewriting history and ignoring its own 1939 non-aggression pact with Nazi Germany.
French President Emmanuel Macron, without mentioning any of the conflicts on display, told the Jerusalem gathering that "no one has the right to invoke their dead to justify division or contemporary hatred".
Netanyahu, in his address to leaders and some 100 Holocaust survivors, said that while for many "Auschwitz is the ultimate symbol of evil... it is also the ultimate symbol of Jewish powerlessness."
The main lesson of the Holocaust, he added, was that "Israel will do whatever it must do to defend our state, defend our people, and defend the Jewish future". "I call on all governments to join the vital effort of confronting Iran," he added.
Israel fiercely opposed a 2015 deal between Iran and world powers that offered Tehran sanctions relief in return for curbs to prevent it from acquiring nuclear weapons, and applauded when US President Donald Trump in 2018 pulled out of the accord.
Netanyahu said Thursday that Israel "salutes" Trump "for confronting the tyrants of Tehran that subjugate their own people and threaten the peace and security of the entire world".
The broader theme of the commemorations was the resurgence of anti-Semitism in Europe and North America. Germany's President Frank-Walter Steinmeier said he bowed "in deepest sorrow" at the memory of "the industrial mass murder of six million Jews, the worst crime in the history of humanity ... committed by my countrymen".
Referring to extremism and intolerance in Germany and elsewhere today, he said: "Of course, our age is a different age. The words are not the same. The perpetrators are not the same. But it is the same evil."
About 100 Holocaust survivors were at the event, among them Yona Amit, 81, who as a child spent the war hiding from the Nazis, and survived - but lost family members including her cousin.
"I exchanged shoes with him" shortly before he was captured, she recalled. "They were straight away sent to Auschwitz. And of course my cousin, with my shoes: straight away up in the chimneys, in the gas chambers," she told AFP. "My shoes are in that big mound of shoes in Auschwitz, my shoes are there. I am here."