The Mercedes star held off his team-mate Lewis Hamilton during the final quarter of the race, after acquiring the lead by attempting a one stop strategy.
However, when his W15 was weighed after the race there was a discrepancy between the original weighing and the one after.
The first weighed the car was measured at the minimum allowance of 798 kg, however when it was weighed afterwards it was found to be 796.5 kg - 1.5 kg under the minimum.
This was then referred to the Stewards who came to a decision, and reported that Russell had been disqualified from the Belgian GP.
The decision has promoted Hamilton to a Belgian GP victory, whilst Piastri obtained P2 and Charles Leclercclinched the final podium spot.
According to the FIA: "Car 63 was weighed on the FIA inside and outside scales with both scales showing the same result of 796.5 kg. The calibration of both scales was confirmed and witnessed by the competitor."
"The Stewards determine that Article 4.1 of the FIA Formula 1 Technical Regulations has been breached and therefore the standard penalty for such an infringement needs to be applied."