Viaduc ferroviaire de Cosne-sur-Loire, Railway bridge in Cosne-Cours-sur-Loire, France

The Viaduc de Port-Aubry is a railway truss bridge over the Loire between Cosne-Cours-sur-Loire and Bannay, 828 metres long with 14 spans of 58 metres on 13 masonry piers. Its riveted steel lattice girders, about a million rivets in all, are heavily rusted; taller lattice sections rise above the deck near the piers. The line was double-track until 1950, then single.

Built by the Compagnie du chemin de fer de Paris à Orléans on the former military line from Bourges to Toul, the viaduct was first crossed by a steam train on 18 December 1893. On 17 June 1940, a French soldier was killed trying to blow it up; German troops then crossed on foot, and planks from local furniture makers were laid over one track for vehicles. In July 1944 the occupier blew up the third span.

Locals call it the "pont du P.-O." after the Compagnie du chemin de fer de Paris à Orléans, which built it on the former military Bourges–Toul line. The name Port-Aubry comes from the nearby lieu-dit on the Nièvre bank, about 60 metres from the bridge. The last train, a grain train from the Saint-Satur silos, crossed in 2000.

The bridge is reached from the Nièvre bank about 60 m from the Port-Aubry hamlet, roughly 3 km south of Cosne-Cours-sur-Loire, or from the Cher side north of Bannay, where the line crosses the Loire lateral canal. The structure is disused since the last grain train in 2000, so it is viewed from the banks and the riverside road rather than crossed. The road bridge at Cosne lies 2.8 km downstream.

The bridge's steel structure holds close to a million rivets, and its 14 spans of 58 metres each rest on 13 masonry piers. In July 1944 the German occupier blew up the third span. The last train to cross, in 2000, was a grain train from the silos of Saint-Satur.