The Landwasser Viaduct (German: Landwasserviadukt) is a single-track six-arched curved limestone railway viaduct. It spans the Landwasser between Schmitten and Filisur , in the canton of Graubünden, Switzerland .

Designed by Alexander Acatos, the Landwasser Viaduct was constructed between 1901 and 1902 by Müller & Zeerleder on behalf of the Rhaetian Railway, which both owns and operates it through to the present day. A signature structure of the World Heritage-listed Albula Railway, it is 65 metres (213 ft) high, 136 metres (446 ft) long; its southeastern abutment connects directly to the Landwasser Tunnel. During 2009, the Landwasser Viaduct underwent renovation work for the first time since its original construction.

The Landwasser Viaduct, composed of dark limestone, forms part of the Albula Railway section between Tiefencastel and Filisur, and is at the 63.070 kilometres (39.190 mi) mark from Thusis.