On the front row in Australia last year, Piastri will need to defy history to be the first local to win in Formula One at Albert Park this season following a chaotic turn of events on Saturday.
After a summer of talk about Mercedes favouritism, Russell and teammate Kimi Antonelli blew the field out of the water in the year's first qualifying session to lock out the front row in Melbourne.
Russell's time of 1:18.518 was 0.785 seconds quicker than Isack Hadjar's Red Bull in third, while Charles Leclerc was fourth for Ferrari before Piastri and teammate Lando Norris.
"We knew as a team we had a really good package between us ... but I don't think we quite thought it was that good," Russell said.
"The whole session felt very good, very tidy, no mistakes. It was just how I wanted to start this weekend.
"We've got a really great engine beneath us, but I also think we've got a really great car beneath us."
Piastri has been among the quickest all weekend at his home grand prix, but Mercedes proved they are the team to beat at the start of 2026 under the new regulations.
"Yesterday probably painted an overly optimistic picture for us," Piastri said, with his McLaren quickest on track on Friday.
"We felt like we were in the mix, and after FP3 (on Saturday) we definitely didn't feel like we were in the mix.
"Our thoughts and the picture (on Friday) were everyone was pretty close. And then Mercedes jumped ahead and the rest was pretty close."
Recent history is now stacked against Piastri, with Kimi Raikkonen in 2013 the most recent driver to win in Melbourne from outside the top three on the grid, when the Finn started seventh.
There was still some chance after qualifying that Piastri could be elevated to fourth, with Antonelli under investigation by the stewards.
A cooling fan was left on the Italian's car in Q3 and eventually fell off the track after he exited the pits and damaged Norris's front wing when the reigning world champion ran over it.
The incident capped a dramatic day for the Italian, who crashed in final practice and left mechanics racing the clock for qualifying.
He then also ruined his first flying lap in the final stage of qualifying with a trip across the grass.
Antonelli was helped in part by Saturday's other huge shock in Max Verstappen, whose crash in the first part of qualifying delayed the session and allowed Mercedes to finish their work.
The four-time world champion is slated to start from 20th on grid after his Red Bull spun under braking on the first corner of his opening flying lap and went nose-first into the barriers.
Carlos Sainz and Lance Stroll will be the only cars behind Verstappen if they are able to make the start after their Williams and Aston Martin cars missed qualifying entirely due to to mechanical issues.
New team Cadillac at least had their drivers Sergio Perez and Valtteri Bottas competing, but they did not progress out of Q1 as the two slowest cars to complete laps.
TOP QUALIFIERS FOR THE AUSTRALIAN GRAND PRIX
1.George Russell (Mercedes)
2.Kimi Antonelli (Mercedes)
3.Isack Hadjar (Red Bull)
4.Charles Leclerc (Ferrari)
5.Oscar Piastri (McLaren)
6.Lando Norris (McLaren)
7.Lewis Hamilton (Ferrari)
8.Liam Lawson (Red Bull)
9.Arvid Lindblad (Red Bull)
10.Gabriel Bortoleto (Audi)
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