A worker at Arrowhead Stadium on Christmas got the shock of her lifetime when Taylor Swift dropped a massive tip … a gesture so shocking, the suite staffer had to frame one of the six fresh Benjamins.

TMZ has learned a viral Facebook post from a stadium employee named Robyn Gentry talking about the superstar’s Xmas generosity is legit … TS indeed tipped $600 to the unsuspecting worker.

As Robyn tells it … TS was at the Christmas game to watch fiancé Travis Kelce play maybe his last NFL game … and superstar was so appreciative of staff working on the holiday, she was handing out her own gifts … that being cold hard cash.

Robyn explained the money was her “whole paycheck for two weeks” and she was so touched, she had to frame one of the bills. Although as of her Sunday post … she still had not spent any of the $600.

Needless to say … it didn’t take long for Swifties to see the post — and make it go viral with shares and comments.