Police are appealing for information following a collision on the A472 between Tredomen and Nelson, which involved two cars.
The collision happened just after midnight – at around 00.10am this morning, Saturday, April 15, and involved a VW Polo and a Mini.
One driver has been taken to University Hospital Wales in Cardiff with life- threatening injures.
If you witnessed the collision or have any information, call 101, quoting log 6 15/4/17.