| Bridge Name: | Wiesen Viaduct |
| Native Name: | Wiesener Viadukt |
| Native Name Lang: | de |
| Official Name: | Wiesener Viadukt |
| Carries: | Rhaetian Railway (RhB) |
| Crosses: | Landwasser |
| Locale: | Wiesen, canton of Grisons, Switzerland |
| Owner: | Rhaetian Railway (RhB) |
| Maint: | Rhaetian Railway (RhB) |
| Designer: | Friedrich Hennings |
| Architect: | G. Marasi (Westermann & Cie, Zürich), P. Salaz and Heinz Studer (RhB) |
| Design: | Arch bridge, Viaduct |
| Material: | Concrete blocks with dimension stone coverage |
| Length: | 210NaN |
| Width: | 3.7NaN |
| Height: | 88.9NaN |
| Mainspan: | 55NaN |
| Spans: | 7 |
| Pierswater: | 0 |
| Builder: | Westermann & Cie, Zürich |
| Begin: | October 1906 |
| Open: | 1 July 1909 |
| Inaugurated: | 1 July 1909 |
| Cost: | CHF 324,000 (1909) |
| Traffic: | 29 passenger trains |
| Coordinates: | 46.6944°N 9.7128°W |
The Wiesen Viaduct (or Wiesener Viaduct; German: Wiesener Viadukt) is a single-track railway viaduct, made from concrete blocks with dimension stone coverage. It spans the Landwasser southwest of the hamlet of Wiesen, in the canton of Grisons, Switzerland.
Designed by the then chief engineer of the Rhaetian Railway, Henning Friedrich, it was built between 1906 and 1909 by the contractor G. Marasi (Westermann & Cie, Zürich) under the supervision of P. Salaz and Hans Studer (RhB). The Rhaetian Railway still owns and uses it today for regular service. An important element of the Davos–Filisur railway, the viaduct is high and long; it has a main span of .
The Wiesen Viaduct forms part of the Davos–Filisur railway section between Wiesen and Filisur. Just southwest of Wiesen railway station, it has, on its south side, a separate pedestrian bridge giving hikers access to Filisur. At the western end of the viaduct is a non functioning Hippsche turning wheel.
The Wiesen Viaduct structure was designed by the then Chief Engineer of the Rhaetian Railway, Henning Friedrich. Construction began in October 1906, under the direction of another engineer, Hans Studer. With the launch of the Davos–Filisur railway in July 1909, the viaduct came into operation. It cost a total of 324,000 Swiss francs to build.
The falsework used for the building of the viaduct was designed by G. Marasi, swallowed up around of wood, and was constructed by the Graubünden carpenter Richard Coray.
In 1926, the viaduct was the inspiration for Ernst Ludwig Kirchner's painting Brücke bei Wiesen.
The Wiesen Viaduct is high and long. Its main span is only wide, but also long, which makes it one of the longest main spans of any masonry bridge.
To the west of the main span are two arches, each long. East of the main span are four more arches, each of them also long.
These technical characteristics combine to make the Wiesen Viaduct the Rhaetian Railway's largest stone and second largest bridge.