Kent Police said officers were alerted at 4.46am on Monday, September 15, to the clockwise carriageway between junction 3 for Swanley and the M20, and junction 4 for Orpington.
Patrols attended the scene along with National Highways officers.
The lorry, understood to be a tipper truck, struck the bridge and spilled hydraulic fluid onto the road surface.
The motorway was closed from junction 3 while the vehicle was recovered and the spillage cleared.
No injuries were reported.
The road has since fully reopened, but long delays were reported throughout the morning as traffic built up.
A Kent Police spokesperson said: “Kent Police was called at 4.46am on Monday 15 September to a report that a lorry had struck a bridge on the clockwise carriageway of the M25 between junctions 3 and 4. Patrols attended the scene alongside Highways officers and the carriageway was closed at junction 3 to allow the recovery of the vehicle. No injuries were reported.”
