Red Bull’s Verstappen appeared to the favourite for pole after setting a blistering pace in the wet conditions, but it was Sainz who stole the headlines with a brilliant lap in his Ferrari to snatch his maiden pole at a sodden Silverstone.
Sainz, who was denied a first victory by Verstappen last time out in Canada, set a time just 0.072s faster than the reigning world champion as he splashed his way to the front of the F1 grid for the first time in his F1 career.
After being informed of his achievement, Sainz said over team radio: "I didn't expect that one. I felt terrible out there! How did I do P1?".
"You keep it together, like a smooth operator," his engineer responded.
Ferrari teammate Charles Leclerc spun on his final lap as he ended up third and 0.315s off the pace.
Half a second behind his Red Bull teammate, Sergio Perez took fourth ahead of Mercedes’ Lewis Hamilton, who was the fastest Brit, one tenth clear of McLaren’s Lando Norris.
Fernando Alonso took seventh for Alpine, ahead of George Russell in the second Mercedes and Alfa Romeo’s Guanyu Zhou.
Meanwhile, Williams’ Nicholas Latifi flourished in the wet conditions as he starred on his way to 10th place in what marked his first-ever Q3 appearance.
Pierre Gasly missed out on a spot in the top 10 in 11th, ahead of Alfa Romeo’s Valtteri Bottas and AlphaTauri teammate Yuki Tsunoda, while Daniel Ricciardo also failed to progress to Q3 with a time only good enough for 14th.
With the rain worsening towards the end of Q2, Esteban Ocon was unable to improve in his Alpine, leaving the Frenchman a lowly 15th on the grid for Sunday’s British Grand Prix.
Williams’ upgraded aero package could not prevent Albon from being knocked out in Q1 in 16th as the Thai racer complained he had no grip on his way to finishing 16th.
Albon was joined in the bottom five by the two Haas and Aston Martin drivers, with Kevin Magnussen 17th ahead of Sebastian Vettel, Mick Schumacher and Lance Stroll, who ended up 20th and slowest.