The Brazilians came into the showpiece in Katowice aiming for a fourth consecutive crown, but they were blown away as the tournament hosts were roared on by their raucous supporters.
Things began well for Brazil, who took the opening set before Poland hit back in fine style, eventually sealing an 18-25 25-22 25-23 25-22 victory.
After Ricardo Lucarelli Santos had saved one match point for Brazil at 24-21, Poland were not to be denied a second time as Mariusz Wlazly finished off an attack to spark scenes of jubilant celebration on the court and amongst the fans in the arena.
The win gained Poland a measure of revenge for the final in Japan eight years ago, when they were beaten in straight sets by their South American rivals.
It represented their second world title, after clinching the 1974 crown in Mexico.
Mateusz Mika led the victory charge with 22 points, while Wlazly contributed 14 and Michal Winiarski and Piotr Nowakowski added 13 and 10 respectively.
Wallace de Souza and Santos ended the match with 18 points each in a losing cause, while Lucas Saatkamp chipped in with 15, including eight blocks.
It was only Brazil's second loss of the competition, with Poland also defeating the defending champions by three sets to two in the third round on Tuesday.
Elsewhere, the bronze was claimed by Germany, who defeated France 25-21 26-24 25-23, their first medal at the championships since the country's unification.