Video of fight at Walt Disney World is spreading across social media like wildfire ... or maybe that should be like "Fire and Ash" ... because the brawl went down outside the Avatar ride.

The viral footage shows folks waiting in line at Disney's Animal Kingdom when they suddenly started popping off at one another ... and then the fists start flying all over the place!

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It's not clear what the heck set this off ... but "Avatar Flight of Passage" is a super popular ride ... and the long-ass wait might have gotten under someone's skin here.

We're out to Disney World to see if anyone got booted ... and if criminal charges are pending ... because police reportedly responded to the incident.

No wonder the Na'vi can't stand humans.