The Italian, who leads the championship from Russell by 25 points, beat Red Bull's Max Verstappen by 0.317secs, even though the four-time champion had the help of a tow from team-mate Isack Hadjar.
McLaren's Lando Norris was an impressive third, 0.440secs back, despite bailing on his final lap, but the world champion has a 10-place grid penalty for exceeding his allowance of engine parts.
Ferrari's Charles Leclerc and Lewis Hamilton were fifth and sixth, ahead of McLaren's Oscar Piastri and the upgraded Racing Bull of British rookie Arvid Lindblad.
Antonelli has looked the man to beat since topping Friday practice and he delivered on his potential with his sixth pole position in 10 races so far this year.
On the slowing down lap, he sent his best wishes to his father Marco, who is celebrating his 61st birthday on Saturday.
Antonelli said: "Q1, I felt a bit lost because the wind picked up and the balance was a bit more on the edge but the session came to us. I changed a little bit the front wing flap for Q2. Q3 was good because we did a decent first lap and second lap I found a lot of time. It was a good lap."
Russell has been struggling to be as comfortable in the medium and high-speed corners in the middle sector, where Antonelli's smoothness has enabled him to not use as much battery energy so he has more for the final sector, where he is making a significant margin on the Briton.
Red Bull employed Hadjar to help Verstappen with a slipstream on the long flat-out section to the final chicane as the Frenchman has a 30-place grid penalty for taking a new engine, which puts him over the limit for the year.
Verstappen said the tow gained him 0.3secs in lap time.
He added: "It was definitely helping me otherwise I would not be standing here, it would be P6 or something.
"Isack, knowing he had a penalty and would be starting at the back, he helped me. I will be looking in my mirrors tomorrow. But we are happy to be on the front row with how we executed it as a team."
Norris and McLaren had not been expecting much when they arrived at Spa, thinking they would continue as the fourth fastest team.
But the car has worked well all weekend and Norris has been especially competitive - he was 0.215secs quicker than Piastri despite not doing a second lap.
"We haven't changed anything, we are just a little quicker here," said Norris, who will start 13th. "It's a shame we are not starting here but there is plenty of opportunity, it is a long race and it's good for overtaking, hopefully we can put on a good show tomorrow."
Leclerc was second fastest after the first runs, just 0.053secs slower than Antonelli, but Ferrari could not maintain that pace and neither he nor Hamilton improved on their second attempts.
Leclerc, winner of the last race at Silverstone, ended up 0.532secs off pole, and just 0.002secs ahead of Hamilton.
Lindblad's pace in the revised Racing Bull - which only he has because there were not enough parts for a second car - was impressive. He ended up just 0.127secs slower than Piastri's McLaren.
Audi's Gabriel Bortoleto and Hadjar completed the top 10, although Hadjar will start 21st after his penalty for using too many engine parts, which is a nominal 30 places.
He is ahead only of Fernando Alonso's Aston Martin - the Spaniard has his own 20-place engine-related penalty.
Top 10
- 1. Kimi Antonelli (Mercedes) - 1:44.361
- 2. Max Verstappen (Red Bull) +0.317
- 3. Lando Norris (McLaren) +0.440*
- 4. George Russell (Mercedes) +0.508
- 5. Charles Leclerc (Ferrari) +0.532
- 6. Lewis Hamilton (Ferrari) +0.534
- 7. Oscar Piastri (McLaren) +0.655
- 8. Arvid Lindblad (Racing Bulls) +0.782
- 9. Gabriel Bortoleto (Audi) +1.267
- 10. Isack Hadjar (Red Bull)*
*Lando Norris and Isack Hadjar both have grid penalties