The collision occurs just before junction 2 northbound and has caused a large amount of traffic and congestion towards J1.
A truck, two cars and a van are believed to have been involved in the crash.
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The M18 is closed in both directions due to a serious collision this evening
National Highways said the M18 is closed in both directions between J1 and J2 between Bramley, near Rotherham, and Wadworth, near Doncaster.
The agency added: “Closed due to a very serious collision. Incident led by South Yorkshire Police.
National Highways added: “This closure is due to a very serious collision. South Yorkshire Police are attending.
“The road is expected to remain closed until at least 11pm tonight for a full investigation to take place.
“Delays are piling up on the approach, with approximately three miles of congestion and delays 20 minutes above normal in both directions.
“Traffic is being diverted.”
Northbound drivers should follow the empty triangle symbol on the A631 westbound towards Rotherham, A6021, A6123 and A630 northbound to the A1M J36 at Warmsworth.
Southbound motorists follow the hollow diamond symbol, along the previous route, but the roads in reverse order.
Delays are likely on detour routes.
South Yorkshire Fire and Rescue said: “A multi-vehicle RTC with no bus is potentially closed on the M18 North between the M1 and M18 J1.
“Severe delays are expected in the Aston and Tinsley areas.”