Lucan Bridge is a road bridge spanning the River Liffey in the town of Lucan in Dublin, Ireland. It joins Lucan's Main Street to the Lower Lucan Road, carrying traffic towards Clonsilla and the north. The bridge is the largest single span masonry arch bridge in Ireland, and is constructed from ashlar masonry with a span of 33 metres (110 feet) and a rise of 6.7 metres (22 feet). It is framed by iron balustraded parapets made by the Royal Phoenix ironworks of Parkgate Street in Dublin.
The first bridge built on this spot was a stone bridge laid down in the later years of the reign of King John (c.1200). A subsequent bridge was built by the first Agmondisham Vesey c.1730, but washed away within very short time. The next was built c.1771, but this too washed away in a flood in 1786 – as did its replacement.