Gardaí are appealing for witnesses to the incident.
A serious collision between a cyclist and a car occurred on the N18 southbound on the Limerick to Ennis road, between Junction 8 and 9.
The cyclist was treated at the scene for serious injuries and has been taken to Limerick Hospital.
It is not yet known what condition the driver of the car is in.
The road is currently closed southbound and diversions are in place.
The road is expected to fully re-open shortly.
Gardaí are appealing for anyone who may have witnessed the collision to contact Ennis Garda Station on 065 6848100.