Català: Marc Ulpi Trajà Nerva (18 de setembre del 53 - 9 d'agost del 117), emperador romà (98 - 117), comunament anomenat Trajà, fou el segon dels anomenats "Cinc emperadors bons" de l'Imperi Romà.
English: Marcus Ulpius Nerva Traianus (18 September 53 – 9 August 117), commonly known as Trajan, was the Roman Emperor from 98 to 117. Born into a non-patrician family in the province of Hispania Baetica, Trajan rose to prominence during the reign of emperor Domitian. Serving as a general in the Roman army along the German frontier, Trajan successfully put down the revolt of Antonius Saturninus in 89. In September 96, Domitian was succeeded by Marcus Cocceius Nerva, an old and childless senator who proved to be unpopular with the army. After a brief and tumultuous year in power, a revolt by members of the Praetorian Guard compelled him to adopt the more popular Trajan as his heir and successor. Nerva died on 27 January 98, and was succeeded by his adopted son without incident.