Gardaí and emergency services are currently at the scene of a road traffic collision at the Moneen Roundabout in Castlebar.
The collision involving a truck and a bike occurred at approximately 8:30am this morning.
The cyclist, a woman aged in her 50s, has been taken to Mayo university Hospital to be treated for injuries which are believed to be serious.
No other injuries have been reported at this time.
The road is currently closed for technical examination and local diversions are in place.