Having drawn each of their previous three Group C matches 1-1, Hansi Flick's side were dominant at Borussia-Park, easily swatting the European champions aside.
Joshua Kimmich got things started in the 10th minute and Germany never looked back, with Thomas Muller netting early in the second half after Ilkay Gundogan had scored from the penalty spot.
Timo Werner's rapid double added further gloss to a mightily impressive victory, as Germany made a statement of intent despite consolations from Wilfried Gnonto and Alessandro Bastoni.
Germany had the bit between their teeth from the off, and although Giacomo Raspadori should have put Italy ahead against the run of play, the hosts had the lead when Kimmich found time in the area to take a touch and side-foot home.
Gianluigi Donnarumma might have done better for Kimmich's opener, but he could do little to prevent Gundogan from doubling Germany's lead from 12 yards after Bastoni inexplicably shoved Jonas Hofmann on the stroke of half-time.
Donnarumma was fetching the ball out of his net again six minutes after the restart. A cross from the left caused havoc in Italy's defense, with Muller's snapshot on the rebound making it 3-0.
A remarkable Manuel Neuer save from Nicolo Barella was rendered meaningless by an offside flag, but a dismal display continued for his opposite number.
While Donnarumma would have been hard pushed to prevent Werner's first goal – a close-range effort from Serge Gnabry's cute lay-off – he was at fault for the striker's second a minute later, playing a dreadful pass that was intercepted by Gnabry, before being fooled by the subsequent finish.
Neuer gave Donnarumma a run for his money with an unusually weak save to gift Gnonto a maiden international goal, with Bastoni heading in a further consolation in stoppage time in a nevertheless humbling defeat for Italy.