The Wiesen Viaduct is a single track limestone railway viaduct. It spans the Landwasser River southwest of the hamlet of Wiesen, in the Canton of Graubünden, Switzerland.

Designed by the then chief engineer of the Rhaetian Railway, Henning Friedrich, it was built between 1906 and 1909 under the supervision of another engineer, Hans Studer. The Rhaetian Railway still owns and uses it today. The viaduct is 88 metres (289 ft) high, 204 metres (669 ft) long, and has a main span of 55 metres (180 ft), which makes it one of the longest main spans of any masonry bridge.