Verstappen’s lap prevented Russell from taking what would have been one of the greatest pole positions in Formula 1 history in the uncompetitive Williams.
Even so, it was a remarkable performance from Russell, who missed out on pole by 0.321 seconds.
Verstappen’s title rival Lewis Hamilton was third fastest in the Mercedes.
And there was a big accident for McLaren’s Lando Norris, who crashed at Eau Rouge in the McLaren in the wettest conditions of the session, bringing out the red flag and leading to a long delay while the rain abated a little.
Norris, who was fastest in the first two sessions, was sent to hospital after initial checks at the circuit for what McLaren called “a precautionary X-ray of his elbow”. He has since been passed fit to race on Sunday.
What about that from Russell?
The laps by Verstappen and Hamilton were impressive by themselves – the Dutchman was 2.6secs quicker than team-mate Sergio Perez in seventh and Hamilton was 2.4secs ahead of his teammate Valtteri Bottas.
But they were both put in the shade by Russell, who underlined yet again why he is regarded as one of the superstars of the future and a hot tip to replace Bottas alongside Hamilton at Mercedes next year.
Russell said: “I was in the fortunate position that I had nothing to lose. We just had to go for it. We saved the full maximum engine mode for the last lap, but [I’m] buzzing, absolutely buzzing. But tomorrow is the important one.”
Hamilton said: “Great job by George. That’s fantastic.”
Pole gives Verstappen a boost as he heads into the race eight points behind Hamilton in the championship, and he now has an opportunity to make amends after a difficult two races in Britain and Hungary.
Verstappen said: “It has been a really tricky qualifying. It has been hard to keep the car on track. And then the long break between Q2 and Q3 it is not easy to settle in again. It is an amazing track to drive but very challenging in the wet.”
A chaotic, fractured session
The session was treacherous throughout as rain hit the demanding Spa-Francorchamps track.
The start of the session was delayed because of heavy rain and all three sessions were held on a wet track.
Norris and Russell excelled through the first two sessions, with Norris setting the pace in the first session from Verstappen by 0.4secs and again in the second from Hamilton by 0.2secs.
The third session started in heavy rain, and Vettel radioed to say it should be red-flagged because the track was too wet – a message meant for race director Michael Masi, emphasized by the German lapsing into an Australian accent when he said: “It’s too wet, mate.”
But Masi ignored him and let the session run. Norris was only the second driver to start a lap, after Russell, and he lost the car as he went through the right-handed part of the swerves.
He over-corrected, the car flicked the other way and he smashed into the barrier on the left-hand side of the track.
Vettel slowed almost to a halt to check Norris was OK, and the Briton could climb out unaided before going to the medical center for the mandatory checks when an accident passes a certain force of impact.
When the final session resumed, there were only six minutes left for flying laps.
Hamilton set the initial pace, 1.5secs quicker than Bottas and a second clear of Verstappen on their first laps.
But then Russell pulled out his magic and looked set for a sensational pole as Hamilton came close, but was just 0.013secs short of beating the Williams.
But Verstappen was still out there. Early in his lap, he was behind Russell but he edged ahead as the lap progressed to snatch pole.
“The car was really on it in these wet conditions and there is so much that has to go right – all the little details to give the driver confidence,” Russell said.
“You have to extract the most. I could put it all on the table and absolutely go for it. I was expecting ninth, eighth, or seventh. Max just pipped me. We are in a great position but [get] no points for qualifying.”