Charles Leclerc took pole position for the Azerbaijan Grand Prix after Lando Norris suffered a huge blow to his title bid as he was eliminated in the first part of Qualifying.
McLaren's Norris is set to start Sunday's race from 16th after he appeared to be hindered by yellow flags during his final flying lap in Q1.
The only slight consolation for the Brit was that world championship leader Max Verstappen could only claim sixth as he was out-qualified by Red Bull team-mate Sergio Perez for the first time in 16 months in a dramatic session.
At the front, Norris' McLaren team-mate Oscar Piastri took second place 0.321s behind Leclerc, whose Ferrari team-mate Carlos Sainz claimed third.
Perez will start fourth in front of Mercedes' George Russell, who endured a lengthy wait after the session before finally escaping with just a reprimand for failing to slow under yellow flags.
Verstappen once more struggled to find a desirable balance in his RB20, while Lewis Hamilton was seventh for Mercedes after another difficult Saturday for the seven-time world champion.
Franco Colapinto reached Q3 in just his second F1 Qualifying, with Aston Martin's Fernando Alonso in front of him and Williams team-mate Alex Albon in 10th.
Albon failed to get the chance to set a final Q3 time in bizarre circumstances after Williams left an engine cooling fan on his car as he exited the garage.
Alpine's Pierre Gasly finished 13th but was later disqualified from Qualifying for exceeding the permitted instantaneous fuel mass flow.
Disaster for Norris
There was lots of confusion about the real reason as to why Norris, who is 62 points behind Verstappen in the championship, bailed out of his lap at the end of Q1.
Track evolution pushed him down the order after he was inside the top 10 following the first runs in qualifying and he soon found himself in the bottom five and needing to improve.
As Norris approached the final braking zone on the lap at Turn 16, there was a brief flashing yellow panel before clearing for white flags on the exit due to Esteban Ocon going slowly.
Norris also ran wide at the exit of the corner before slowing down on the flat-out run to the line. The team immediately apologised to him on the radio but it is not clear if this was because they made a mistake by telling him to abort his lap.
"Everyone did their second laps and I didn't. It was unlucky, that's all. I had to lift," he told Sky Sports F1.
In the context of the title race, it could be a huge moment as Norris has taken points out of Verstappen in the last two races and McLaren have a stronger car than Red Bull.
The British driver will need help from Safety Cars or red flags on Sunday to get anywhere near the top positions but will likely have to limit the damage.
"It is what it is. There's a long race ahead, we have some good tyres in the bank, I'm still hopeful we can get a good result. I think the car is quick. Bit frustrating, but nothing I can do," he said.
Norris got a slight boost after the session as his qualifying position of 17th was boosted a place by Gasly's disqualification.
Verstappen has rollercoaster qualifying
When Verstappen topped Q2, it felt like he smelt blood after Norris' elimination and would be in the fight for pole.
However, a big slide at Turn 16, which leads to a 2.2km flat out section, cost him time on the first Q3 runs and he didn't improve with his second effort, so ended up 0.658s behind pole-sitter Leclerc.
"Somehow in (Turn) 16 just suddenly became very loose mid-corner and that caught me out on the first run in Q3," Verstappen told Sky Sports F1.
"I bottomed out on the kerb as well, so that's literally the worst corner where that can happen."
Verstappen was outqualified by Perez for the first time since the 2023 Miami Grand Prix in May last year.
Red Bull didn't have the best long run pace on Friday, so Verstappen could have a similar experience to Monza two weeks ago when he finished in sixth.
"We made some changes going into qualifying which made it a lot harder to drive and not so connected with the tarmac. Then we tried to find solutions throughout qualifying," said Verstappen.
"Today we didn't optimise it. I mean, we tried to perfect the car. You look into details where you think you can do better."
Leclerc reigns supreme on Saturday in Baku again
The Baku City Circuit is arguably Leclerc's strongest track on the calendar, having taken every pole for the Azerbaijan Grand Prix since 2021.
Leclerc was fastest in Q1, second in Q2, then had two laps good enough for pole in Q3. He first did a 1:41.610 before improving to a 1:41.365 which put pole out of reach.
With Verstappen only in sixth, Leclerc has a chance to take a big chunk of points out of his 86-point deficit to the reigning world champion.
"It's one of my favourite tracks of the season, I really like it," said Leclerc.
"It hasn't been an easy weekend because obviously the crash in FP1. But it didn't make me lose the confidence, I knew the pace was there.
"In FP2 we had a problem with a new part on the car and we lost another half an hour and we didn't recover those laps, but the pace was always there.
"In qualifying, it was all about trying to stay away from the walls and then in that last lap I went for it a bit more and the lap time came very nice. The car felt really good, everything felt great and it's amazing to be on pole."
Piastri managed to split the Ferraris with a great effort at the end of Q3 after McLaren looked like they were on the backfoot in the other phases of qualifying.
Mercedes' Russell was half a second off pole but out-qualfied team-mate Hamilton for a 13th time this year, so has won the qualifying head-to-head.
Having had a strong Friday, Hamilton was never near the front in final practice and qualifying itself on Saturday.
Sky Sports F1's live Azerbaijan GP schedule
Sunday September 15
8.30am: F2 Feature Race
10:30am: Grand Prix Sunday: Azerbaijan GP build-up*
12pm: The AZERBAIJAN GRAND PRIX*
2pm: Chequered Flag: Azerbaijan GP reaction
3pm: Ted's Notebook
*also live on Sky Sports Main Event
Formula 1 leaves mainland Europe for Baku and the Azerbaijan Grand Prix this weekend, live on Sky Sports F1. Stream every F1 race and more with a NOW Sports Month Membership - No contract, cancel anytime
