The Melbourne teenager, who has strong family ties to Shepparton, won a Sprint race in the opening round of the F2 season at Bahrain's International Circuit.
It was the youngster's debut outing in F2 — the feeder class to F1 — following his F3 championship success last year.
Piastri, 19, edged out his experienced rivals in a heart-stopping race that was decided on the final lap.
The Prema racing driver completed a stunning last-lap overtake against Guanyu Zhou, with eventual second place-getter Christian Lundgaard also challenging behind — as the trio went three-wide down the pit straight and dived into the first of 15 corners.
On a new set of soft compound tyres, Piastri held off his two competitors and crossed the chequered flag to seal a memorable victory.
“Regardless of whether it's the second race or the last race I complete in F2, that's got to go down as the craziest race I've ever had, and the craziest victory I've ever had,” Piastri said post-race.
“I can't thank the team enough, obviously the pit stop at the end was the right move.
“Then I made some good moves and put myself in a good spot, and here we are on the top step.”
The performance of the Alpine Academy driver in the second race of the weekend followed his impressive fifth finish in race one.
Those two results left Piastri leading the F2 championship ahead of the weekend's feature race on Sunday.
But his hopes of adding a second win to his belt were dashed late in the race.
After displaying his skilful overtaking ability throughout the race, Piastri was challenging for second spot with only a handful of laps left until the chequered flag.
However, Piastri found himself under pressure from Britain driver Dan Ticktum and the two came together on turn two with three laps remaining.
Piastri spun out and was unable to finish the race, with the emerging star letting slip of his championship lead and falling to fourth place.
Shepparton supporters of Piastri will have to wait until May 20-22 to see the young gun fire up his F2 machine when the season heads to Monaco for round two.
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