The left-arm pacer scripted history by becoming the first bowler from New Zealand to claim a World Cup hat-trick.
Boult produced a magical spell of fast bowling in the last over of Australia's first innings as he scalped a well settled Usman Khawaja, Mitchell Starc and Jason Behrendorff in successive deliveries to achieve the unique feat.
Bolt (4/51 in 10 overs) struck after Khawaja and Alex Carey (71 off 72 balls) scored contrasting half-centuries to lift Australia from a disastrous start after they opted to bat. Boult's hat-trick was the second off the ongoing ICC World Cup after Indian seamer Mohammad Shami achieved the feat against Afghanistan.
Boult's hattrick eventually went down in a losing cause as Mitchel Starc produced yet another fiery spell to pick up a Fifer against the Black Caps and help Australia inflict a 86-run win over their arch rivals.
With his swinging full-pitched deliveries, Boult sent back the well-settled Usman Khawaja (88 off 129 balls), Micthell Starc and Jason Behrendorff, while giving away just two runs at the Lord's.
The defending champions lost half their side with less than 100 runs on the board, but a 107-run partnership for the sixth wicket between Khawaja and Carey helped them rebuild. It was a rare occasion when the opening duo of David Warner and Aaron Finch, in red-hot from entering this game, failed to fire.
While Finch (8) was the first to go, trapped in front by the experienced Trent Boult, Warner departed after making 16 to leave Australia in a spot of bother at 38 for two in the 10th over, and it became worse when Steve Smith was sent back by Lockie Ferguson with the scorecard reading a precarious 46 for three in the 12th over.