The single-vehicle crash happened near Junction 45 Ynysforgan last night
One person's died following a single-vehicle crash on the M4.
The collision, involving a Ford KA, happened at around 19:10pm on the Eastbound carriageway between junction 46 Llangyfelach and 45 at Ynysforgan.
The driver was taken to Morriston Hospital for treatment, but the front-seat passenger sadly died.
The stretch of road was closed for several hours while emergency services attended the scene.
South Wales Police spokesperson said, "We would like to thank motorists in the area at the time for their patience and understanding.
"We are appealing for witnesses to the collision or to the manner of driving of the Ford KA prior to the collision.
"Any witnesses are asked to contact police on 101 qouting occurrence reference 1800030617."