Russell's Italian teammate and Formula 1 championship-leader Kimi Antonelli, chasing a sixth win in a row on Sunday, qualified third with McLaren's world champion Lando Norris fourth.
Mercedes have taken pole in all seven F1 races so far in 2026, winning them all, and Saturday was Russell's third of the season to 19-year-old Antonelli's four -- a morale boost for the Briton as he seeks to bounce back from two races without scoring.
"Nice to feel in the groove again," said Russell over the team radio after lapping 0.064 of a second quicker than compatriot Hamilton for a 10th career pole ahead of what will be his 100th grand prix for Mercedes.
"It's been a great weekend so far. I feel like my old self again where every lap I'm doing the job, always fighting in those top positions," he added later.
"The last few races for numerous reasons haven't quite been on our side but I came in this weekend with a clean slate, felt good and it's great to be on pole."
The final phase of qualifying was briefly halted after Ferrari's Charles Leclerc crashed into the tyre wall at turn four.
Leclerc clambered out and walked away after his third crash in eight days, with incidents in both qualifying and the race at his home Monaco Grand Prix last weekend.
He will start 10th, unless changes to the engine and gearbox are required.
Hamilton was fastest in the first phase, ahead of Russell and Leclerc, and will be chasing his first win since 2024 and first for Ferrari.
The Red Bulls of Max Verstappen and Isack Hadjar qualified fifth and sixth, with Oscar Piastri, last year's winner from pole, seventh for McLaren.
Racing Bulls' Liam Lawson starts eighth with Nico Hulkenberg ninth for Audi.
Double world champion Fernando Alonso qualified last for Aston Martin ahead of what is likely his final Barcelona appearance, with the race off the calendar next year and the 44-year-old Spaniard out of contract at the end of the season.