Peillat scored from penalty corners in the 43rd, 52nd and 59th minutes, while 'Player of the Match' Niklas Wellen (60th) struck with just a few seconds left in the game to stun Australia.
Star drag-flicker Gonzalo Peillat struck a second-half hat-trick as Germany made a sensational comeback after being two goals down to beat Australia 4-3 and enter the FIH Men's World Cup final for the fifth time in Bhubaneswar on Friday. (More Hockey News)
Peillat scored from penalty corners in the 43rd, 52nd and 59th minutes, while 'Player of the Match' Niklas Wellen (60th) struck with just a few seconds left in the game to stun Australia, who squandered a 2-0 half-time lead in the semi-final at the Kalinga Stadium.
Jeremy Hayward (12th), Nathan Ephraums (27th) and Blake Govers (58th) scored for Australia, who will now play for the bronze medal on Sunday.
This was Germany's second comeback win after being 0-2 down against England as well in the quarter-final match. They had scored twice in the last three minutes to equalise and then beat England in penalty shootout to enter the semi-finals.
Two-time champions Germany recorded their first entry into the final after the 2010 edition in New Delhi, where they had finished runners-up. They had won the silver medal in 1982 as well before winning the titles in 2002 and 2006.
Germany also took revenge for their 1-3 loss to Australia in the Tokyo Olympics semi-finals.
For three-time champions Australia, this was their second consecutive failure to enter the final. They had lost to the Netherlands at the same stage in 2018, finishing with a bronze after consecutive titles in 2010 and 2014.
Australia were leading 2-0 till the 42nd minute and it looked like they would run away with the match but the three drag-flick goals from Peillat, who has played more than 100 matches for Argentina and won the 2016 Rio Olympics gold for the Las Leonas but is now a German citizen, changed the complexion of the game.
Australia took the lead in the 12th minute from the second penalty corner they earned with Jeremy Hayward cementing his position at the top of the goal-scoring chart. He sounded the board by sending the ball to the left of goalkeeper Alexander Stadler.
A few seconds later, Stadler made a miraculous save by blocking a shot from Tim Brand.
Australia goalkeeper Andrew Charter too was tested in the second quarter as he palmed away a stinging drag-flick from Tom Grambusch off a penalty corner.
Germany exerted more pressure in the second quarter and entered the Australian 'D' several times but they could not create a clear opening. The Australians also won three video referrals against penalty corner decisions.
It was the Germans who were attacking all along but Australia needed just one counter attack to double their lead three minute from half time.
Lachlan Sharp found acres of space inside the German circle after a long ball from Australia's deep defence searched him out. He sent a cross for Nathan Ephraums to make a one touch before pushing it past Stadler, who was doing a fantastic job under the German goal.
Misfortune for Germany continued as a penalty stroke awarded to them in the third minute of the third quarter was overturned after Australia took a video referral.
Australia got a golden chance to increase their lead in the 42nd minute but Jake Whetton's push from the middle of the striking circle went wide.
Germany were not to be denied for long after they earned five back-to-back PCs. Gonzalo Peillat finally sounded the board to pull one back for the European side.
The German siege of the Australian citadel continued and Flynn Ogilvie made a goal-line save in the 53rd minute before goalkeeper Charter did the same with a few seconds left in the quarter.
The German onslaught continued as Peillat scored his second goal of the match from their 12th PC of the day, sending a high flick into the goal.
Drama unfolded towards the end of the match as Blake Govers gave Australia a 3-2 lead in the 58th minute from his drag-flick. But Germany responded the next minute with Peillat completing his hat-trick from a penalty corner as the scores were level at 3-3.
With less than 20 seconds left in the match, Niklas Wellen, the lynchpin of the German attack, fired the ball home to seal a famous win for the Die Honamas.