Susan Sarandon left the NYC Netanyahu protest in cuffs Thursday ... for participating in the demonstration against the Israeli prime minister's speech.

Video from the protest shows the massive crowd -- including the actress -- chanting ... "Netanyahu, you can't hide! We charge you with genocide."

Several people were holding up red banners while Susan and the other activists wore shirts that said "Fund people not bombs."

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Susan wasn't the only actress detained -- "Hacks" star Hannah Einbinder was also led away by officers, yelling ... "Free Palestine! Get Netanyahu out of New York!"

Other celebs were spotted protesting, like Elliot Page, who was seen sitting with the crowd and holding up a banner in solidarity.

The demonstration is playing out ahead of Netanyahu's speech at the United Nations.

Hundreds of protesters gathered, forcing streets to close.