A 21 year old man from Burry Port has been arrested on suspicion of a serious assault. He remains in police custody as police investigate.
The incident happened outside The Shaker nightclub, Island Place, Llanelli at approximately 12.45am on Sunday, February 26.
A man was seen to get out of a vehicle, assault the man, who is in his thirties, then get back into the vehicle and drive away.
Ambulance and police were called to the scene. The victim suffered a serious head injury and is in a critical condition in hospital.
Police are appealing for witnesses to come forward to assist with the investigation.
Anyone with information is urged to contact the incident room Llanelli CID on 101.