The collision, between a cyclist and a red Seat Ibiza, took place around 2pm on Saturday (9 March).
The female cyclist tragically died at the scene of the accident.
The male driver of the Seat car was arrested on suspicion of causing death by dangerous driving.
The road was closed overnight while Police accident investigators were at the scene.
Dyfed Powys Police are now appealing for anyone who may have seen the accident, or who may have dashcam video footage to get in touch.
A spokespersojn for Dyfed Powys Police said: “The red car had travelled along the B4306 from Pontyberem in the general direction of Hendy, while the cyclist was travelling towards the general direction of Llannon.
“Tragically, the 31-year-old cyclist died at the scene. Our thoughts are with her family, who are being supported by specialist officers.
“The Tirbarch Farm and Y Geibren stretch of the B4306 between Hendy and Llannon was closed overnight.
“The car driver was arrested on suspicion of causing death by dangerous driving. He has been released under investigation while police enquiries continue.
“The investigation team is appealing for witnesses who may have information to get in touch. They are particularly keen to see dashcam, doorbell and CCTV footage of the red Seat Ibiza before the collision.”
(Lead image: Google maps)
