Oscar Piastri delivered a hammer blow to Lando Norris's bid to win back-to-back races by seeing off his title rival to take a commanding pole position for the Spanish Grand Prix.
Piastri holds a three-point championship lead over Norris, and the Australian delivered in qualifying to beat the British driver by an impressive 0.209 seconds at Barcelona's Circuit de Catalunya - the biggest pole margin of the season so far.
World champion Max Verstappen took third place for Red Bull, one spot clear of Mercedes' George Russell. Verstappen and Russell set identical times with the former taking the higher grid slot after setting his time first.
Lewis Hamilton qualified fifth with Kimi Antonelli sixth for Mercedes and Charles Leclerc, who completed just one quick lap in Q3, seventh.
McLaren have won six of the eight rounds so far, and their rivals might have hoped that a clampdown on flexible front wings - which some believe has contributed to the British team's rise - would slow them down. However, the rule tweak has done little to influence McLaren's speed, with Piastri and Norris embroiled in a tense battle for pole.
Norris secured top spot in Monaco a week ago before going on to claim his first win since March's season-opening round in Melbourne.
He ended the first runs here in Q3 holding a slender 0.017 sec margin over his team-mate. Norris enjoyed a tow off Piastri's McLaren with the Australian calling his team-mate's antics "cheeky".
It wasn't the perfect lap. It is going to be an interesting one tomorrow and I am pretty glad I am starting from pole.
The McLaren duo returned for a final shot at pole and although Norris improved on his first lap, it was Piastri who lit up the timesheets by taking his fourth pole of the season by two tenths.
"I am very happy," said Piastri. "It didn't start off in the best way. I was struggling but I found pace and the car has been mega.
"I improved quite a lot in Turn 1 on my second lap and it all came together. It wasn't the perfect lap. It is going to be an interesting one tomorrow and I am pretty glad I am starting from pole."
Norris said: "Oscar drove very well. The pace was there but I made a few mistakes."
Hamilton called his car "undriveable" in practice on Friday, but he will take comfort from out-qualifying Leclerc for the first time since the second round in China, albeit half-a-second back from Piastri.
Home favourite Carlos Sainz qualified a disappointing 18th while Red Bull's Yuki Tsunoda will prop up the grid after he clocked the slowest time with just eight tenths separating first to last in Q1.
British rookie Ollie Bearman progressed to Q2, and will line up from 15th, two places clear of Esteban Ocon in the other Haas.
