The Maria Pia bridge (Ponte Maria Pia), commonly known as Ponte Dona Maria, is a railway bridge built in 1877 by Gustave Eiffel in Porto, Portugal. Built of wrought iron, its two-hinged crescent arch used to carry the railway, before a modern bridge was constructed in 1991, to Lisbon for 353m across the River Douro at a height of 60m.
Eiffel's design was the least expensive of eight entries into an 1875 competition, being 31% less than the next lowest priced. The bridge was built to avoid a 12 km detour, and started on 5 January 1876 and completed on 4 November 1877. At that time its span of 160m was the longest arch bridge in the world, the previous record holder, at 156m, being the Eads Bridge over the Mississippi at St Louis. The bridge was opened by the king of Portugal and named after his queen Maria Pia.
In 1991 the bridge was superseded by the new St John (Ponte de São João) bridge, designed by engineer Edgar Cardoso.