The Loopline Bridge (or the Liffey Viaduct) is a railway bridge spanning the River Liffey and several streets in Dublin, Ireland. It joins rail services from south of Dublin to Connolly Station and lines north.
Designed by John Chaloner Smith, the bridge was built in 1891. It consists of wrought iron lattice girders on a double row of piers with five spans. The viaduct is approximately six metres above street level and supports two railway tracks.
During original planning and construction (in the late 19th century) the project was subject to much opposition and controversy, because the structure blocks the view down river to The Custom House. However, the bridge was deemed necessary as a rail link between north and south Dublin, and to facilitate the movement of transatlantic mail coming from Kingstown (Dún Laoghaire) and Queenstown (Cobh).
100 years later, the visage of the bridge remains the subject of some debate. Already arguably less attractive than some of Dublin's other bridges, the façades of the Loopline have been used by Iarnród Éireann for billboard advertising. As of 2006, the company has scaled back the bridge's use for this purpose to reduce impact on the city skyline, following input from An Bord Pleanála and Dublin City Council.