Alcántara is a municipality (pop. 1769) in the province of Cáceres, Extremadura, Spain, on the Tagus, near Portugal. It is famed for its Roman bridge of six symmetrical arches, 194 m/670 feet long and 71 m/210 feet high, built in honour of Trajan in 103-106. An inscription gives the name of the architect of the viaduct, C. Iulius Lacer. The bridge carried the Roman road from Norba to Conimbriga.
The Order of Alcántara, a religious and military order, was established in 1176 here, for defence against the Moors, and was suppressed in 1835.