Protesters marched through the Iran-backed Shiite movement's south Beirut bastion, carrying banners reading "Jerusalem, Eternal Capital of Palestine" and "Jerusalem is Ours".
Hezbollah chief Hassan Nasrallah had called for the mass demonstration last week after US President Donald Trump decided to upend decades of diplomatic protocol by recognising Jerusalem as the capital of Israel.
The move has been widely condemned and sparked days of protest across the Middle East.
Israel fought a devastating war against Hezbollah in Lebanon in 2006 that killed more than 1,200 Lebanese, mostly civilians, and 120 Israelis, most of them soldiers.
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"All Arab peoples must repeat with the Palestinian people: 'We will be millions of martyrs to sacrifice for Jerusalem'," he said, a pledge echoed in unison by the crowd numbering tens of thousands.
Israel withdrew its forces from southern Lebanon in 2000, ending a 22-year occupation, but the two countries remain technically at war and there have been occasional skirmishes on the border.
"We're the children of Hezbollah, of course we're ready to fight," he said.
The rally was held under tight Hezbollah security and passed without incident, a day after a much smaller protest turned violent near the US embassy on the outskirts of Beirut.
Yesterday, several people were lightly wounded, including an AFP photographer, when Lebanese security forces responded to stone throwing with tear gas, water cannon and rubber bullets.
The few hundred protesters, mostly from Palestinian, leftist and Islamist parties, were blocked by a metal gate on the road leading to the highly-protected US embassy.
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