Saint John Harbour Bridge, Steel bridge at Saint John Harbour, Canada

The Saint John Harbour Bridge is a hollow box, haunched girder structure crossing Saint John Harbour at the mouth of the Saint John River. It carries four traffic lanes over three spans of 125, 250 and 125 metres, resting on four main piers.

The Saint John Harbour Bridge opened on 17 August 1968 as part of the Saint John Throughway project, built by the National Harbours Board with federal, provincial and municipal funding. It was a new harbour crossing, not a replacement for an older bridge; proposals for such a crossing dated back to an 1874 debate in the House of Commons. Its construction closed Navy Island's status as an island and led to the demolition of the neo-gothic Union Station.

The construction of this bridge modified the landscape of Navy Island and led to significant changes in the maritime navigation patterns of Saint John Harbour.

The bridge is accessible daily and offers views of the harbour and river from multiple angles. Visitors interested in the structure can observe it from nearby waterfront areas and various vantage points throughout the city.

The structure uses a hollow box girder design that represented modern engineering when it was built. This engineering approach allowed the bridge to span the river efficiently with its three distinct sections.