The Briton’s 92nd career pole was won by just 0.059 seconds, but the battle for P1 fizzled out when neither Hamilton nor Bottas could improve their times with their second laps in the top-10 shootout.
High track temperatures of around 50°C put a premium on tyre preparation, and though several drivers failed to find time at the end of the session, both Mercedes drivers lamented second laps that were simply scrappy.
“Physically it’s tough,” Hamilton said. “It’s so fast - the fastest we’ve ever been around here.
“I couldn’t go quicker on my second lap. I thought I could, but it just wasn’t a great lap - but the first one was decent, I guess, which did the job.”
Pole is a strong indicator of success at the Circuit de Barcelona-Catalunya, with 21 winners from 29 races coming from pole and only a further five from second place.
Bottas, third in the championship and 34 points behind Hamilton, said he was eyeing turn one as his best chance to snatch the lead and make inroads on the Briton’s points lead.
“I think the start will be the best opportunity for me,” said the Finn. “Again, on Friday my long runs were competitive, so I will have the pace, but the start will be the best chance.”
Max Verstappen qualified third and 0.7 seconds off the pace but is relying on Red Bull Racing’s impressive race pace from Friday practice to catapult him into the battle with Mercedes today.
“I felt happy in the car,” he said. “I just hope I can apply a bit of pressure.
“I know it’s very hard to overtake around here, but we’re going to try everything we can to be close to them and make it a bit difficult.”
Racing Point teammates Sergio Perez, returning from two weeks in COVID-19 isolation, and Lance Stroll qualified fourth and fifth around 0.2 seconds behind Verstappen.
The pink cars, currently the subject of legal action in the FIA International Court of Appeal for copying Mercedes’s brake ducts, are aiming for the podium in the race but look likely to be competing in a class of their own behind the top three but ahead of the midfield.
Thai driver Alex Albon qualified sixth, extending his run of poor qualifying form relative to Red Bull Racing teammate Verstappen.
Albon was 1.4 seconds off pole and 0.7 seconds slower than the sister car, comfortably the largest gap between the two this season when both have qualified in the top 10.
McLaren teammates Carlos Sainz and Lando Norris locked out the fourth row of the grid in seventh and eighth respectively.
Charles Leclerc qualified ninth for Ferrari, only 0.049 seconds ahead of AlphaTauri’s Pierre Gasly in 10th.
Leclerc’s teammate, Sebastian Vettel, missed out on the top-10 shootout for the third time this season, knocked out in 11th by 0.002 seconds.
The Ferrari driver fractionally beat AlphaTauri’s Daniil Kvyat by 0.024 seconds.
Daniel Ricciardo was Renault’s highest-placed driver in 13th, the Australian beating teammate Esteban Ocon by two places and more than 0.3 seconds.
Kimi Raikkonen split the Renault pair in 14th for Alfa Romeo’s first top-15 appearance of the year.
Kevin Magnussen was knocked out of Q1 in 16th but complained he was obstructed on his final flying lap. The Dane will see the stewards post-qualifying for a blocking incident involving Daniil Kvyat.
His Haas teammate, Romain Grosjean qualified 17th and almost 0.2s behind. The Frenchman apologised to his team for the poor result considering his car required an overnight internal combustion engine change to repair a leak.
Williams teammates George Russell and Nicholas Latifi qualified 18th and 19th after of Alfa Romeo’s Antonio Giovinazzi at the back of the grid.