The Loughor railway viaduct is a railway viaduct carrying the West Wales Line across the River Loughor. The original structure was built completely in timber and was engineered by Brunel and K. E. Fletcher. The timber was later replaced with wrought iron, and then with steel plate. It is currently a Grade II listed structure. The structure is in striking contrast to the adjacent Loughor road bridge.
The Loughor viaduct dates from circa 1860 and was built to carry two tracks. The viaduct sits on a file mile section of track between Cockett and Duffryn which was reduced to single track operation in 1986 to save on maintenance costs. The aging structure is due for renewal in 2012/2013. There are proposals to re-double the section of track along with the brige renewal to reduce service bottlenecks in the area.