Piastri headed affairs from George Russell and Charles Leclerc, the leading two drivers both dipping below the 1:16 marker.
Such was Piastri’s pace, that his best lap was just 0.006s slower than the fastest ever lap set around Albert Park – a lap set by Max Verstappen in qualifying last year.
However, the session highlighted how closely matched the top four teams are, with little between Red Bull, Mercedes, Ferrari, and McLaren.
Russell, Verstappen, and Piastri all had spells at the top of the timesheets, with Leclerc within touching distance on single lap pace.
It paints an immensely competitive picture heading into qualifying, even more so than was expected amid suggestions McLaren was half a step clear of the pack.
After three practice sessions, that doesn’t seem to be the case, though a mistake on his best lap masked Norris’ true pace.
Even Williams showed impressive speed, with Carlos Sainz sitting fifth and faster than Lando Norris for much of the session before sliding to 11th at the chequered flag. Alex Albon in the other car was 12th.
If Williams looks a dark horse, Racing Bulls should also be considered as much.
Yuki Tsunoda was an encouraging ninth, following on from a strong performance in Free Practice 2 on Friday.
If nothing else, it demonstrates that the midfield is now hanging on to the coattails of the leading contenders.
Jack Doohan ended the hour behind Alpine teammate Pierre Gasly, his 0.25s deficit an acceptable margins within the team in what must again be considered a positive hour for the young Aussie.
Meanwhile, Lawson endured a difficult session as he logged only two laps – without setting a time – before returning to the garage for an extended period.
Red Bull subsequently revealed a power unit problem.
The Kiwi didn’t get back out and will head into his first qualifying session around Albert Park with a third less running than he’d hoped for.
It could have been worse, as Oliver Bearman learned when he drew the red flags just seconds into the session.
The Haas driver dropped a wheel under braking into Turn 11, spinning him into the gravel trap without a time to his name.
It marked a disastrous start for the young Brit after crashing out of opening practice on Friday, inflicting damage that kept him out of Free Practice 2 as the team repaired his car.
The consolation, if there was any, was that the car didn’t reach the barrier and is at no risk of missing Qualifying later today.
With practice complete, the next session is qualifying, with four teams holding a realistic shot at pole position.
The qualifying hour begins at 16:00 AEDT.
| Pos | Num | Driver | Team | Laps | Diff | Best |
| 1 | 16 | Charles Leclerc | Ferrari | 31 | 1:16.439s | |
| 2 | 81 | Oscar Piastri | McLaren – Mercedes | 29 | 0.124s | 1:16.563s |
| 3 | 4 | Lando Norris | McLaren – Mercedes | 29 | 0.141s | 1:16.580s |
| 4 | 22 | Yuki Tsunoda | Racing Bulls – Honda | 28 | 0.345s | 1:16.784s |
| 5 | 44 | Lewis Hamilton | Ferrari | 30 | 0.420s | 1:16.859s |
| 6 | 6 | Isack Hadjar | Racing Bulls – Honda | 29 | 0.580s | 1:17.019s |
| 7 | 1 | Max Verstappen | Red Bull – Honda | 21 | 0.624s | 1:17.063s |
| 8 | 27 | Nico Hulkenberg | Sauber – Ferrari | 23 | 0.722s | 1:17.161s |
| 9 | 18 | Lance Stroll | Aston Martin – Mercedes | 27 | 0.840s | 1:17.279s |
| 10 | 63 | George Russell | Mercedes | 29 | 0.843s | 1:17.282s |
| 11 | 55 | Carlos Sainz | Williams – Mercedes | 29 | 0.863s | 1:17.302s |
| 12 | 23 | Alex Albon | Williams – Mercedes | 27 | 0.863s | 1:17.302s |
| 13 | 14 | Fernando Alonso | Aston Martin – Mercedes | 26 | 0.891s | 1:17.330s |
| 14 | 7 | Jack Doohan | Alpine – Renault | 29 | 0.955s | 1:17.394s |
| 15 | 10 | Pierre Gasly | Alpine – Renault | 29 | 1.054s | 1:17.493s |
| 16 | 12 | Kimi Antonelli | Mercedes | 30 | 1.195s | 1:17.634s |
| 17 | 30 | Liam Lawson | Red Bull – Honda | 29 | 1.201s | 1:17.640s |
| 18 | 5 | Gabriel Bortoleto | Sauber – Ferrari | 28 | 1.408s | 1:17.847s |
| 19 | 31 | Esteban Ocon | Haas – Ferrari | 30 | 1.595s | 1:18.034s |
| 20 | 87 | Oliver Bearman | Haas – Ferrari |
