George Russell had led Lewis Hamilton home in a Mercedes one-two after he opted for a one-stop strategy.
Mercedes driver George Russell has been disqualified and lost his Belgium Grand Prix win on Sunday, after his car was found to be underweight, and his teammate Lewis Hamilton was promoted to first place.
Initially the car had been found to be compliant but the technical delegate's report said that the car had not been fully drained of fuel.
The car was weighed again on the FIA inside and outside scales with both showing the same result of 796.5 kilograms, 1.5 kilograms below the minimum weight required and all other drivers move up one place in the classification.
"During the hearing the team representatives confirmed that the measurement is correct and that all required procedures were performed correctly," the governing FIA said in their release.
"The team also acknowledged that there were no mitigating circumstances and that it was a genuine error by the team."
Russell had led Hamilton home in a Mercedes one-two after he opted for a one-stop strategy.
The decision means that McLaren's Oscar Piastri finishes second with Ferrari's Charles Leclerc in third.
"We have to take our disqualification on the chin. We have clearly made a mistake and need to ensure we learn from it," Mercedes team boss Toto Wolff said.
"We will go away, evaluate what happened and understand what went wrong. To lose a one-two is frustrating and we can only apologise to George who drove such a strong race.
"Lewis is of course promoted to P1, he was the fastest guy on the two-stop and is a deserving winner."
The inherited win means Hamilton has now won the Belgian Grand Prix five times, drawing level with Ayrton Senna and one behind Michael Schumacher who holds the record with six wins at Spa.
The decision is a devastating one for Russell, who thought he had won his second race of the season, and was hailed by Wolff as the "tyre whisperer" after he opted to stay out after one pit stop and held off Hamilton to the chequered flag.
"Heartbreaking... we came in 1.5kg underweight and have been disqualified from the race," Russell posted on Instagram.
"We left it all on the track today and I take pride in crossing the line first. There will be more to come."
Instead, it is Hamilton who now has two wins from the last three races, now the only driver apart from championship leader and triple world champion Red Bull's Max Verstappen to win more than one race this season.
Verstappen moves up to fourth place, and with his closest rival, McLaren's Lando Norris, finishing one place behind him, his overall lead remains at 78 points.
Piastri's promotion to second does mean McLaren now go into the four-week break 42 points behind Red Bull in the constructors' championship.
Verstappen began the race 11th on the grid after a 10-place grid penalty for taking on a fifth engine, and was unable to win his fourth successive Belgian GP. He has now gone four races without a win, the first time that has happened since 2020.
