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Ring the opening jingle bells ... because this holiday season brought out the worst in a group of Nantucket shoppers -- leading to a brawl in the streets!

Video taken over the weekend is now circulating online ... and it kicks off with a group of people in an argument outside the Nantucket Christmas Stroll, an annual outdoor market complete with a tree lighting and visit from Saint Nick himself.

After some pushing, pulling, and arguing, all hell breaks loose when someone appears to throw a punch -- and another guy jumps on his back to stop him.

The brawler, who flew as high as Rudolph on Xmas night, pulls the other dude back and throws him into the street ... but a bunch of that guy's buddies run up to him, seemingly ready to throw hands. Eventually, some people get in b

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