7 people have been taken to Cork university hospital with injuries.
It involved a truck and four cars.
It happened at the Killarney roundabout in Mallow at around 1pm this afternoon.
The N20 Cork/ Limerick Rd remains closed this evening both ways at the Annabella Rounabout in Mallow and diversions are in place.
Gardai say traffic is heavy and motorists are being advised to avoid the area.