The Pons Sublicius is the earliest known bridge of ancient Rome, spanning the Tiber River near the Forum Boarium downstream from the Tiber Island, near the foot of the Aventine Hill. According to tradition, its construction was ordered by Ancus Marcius around 642 BC, but this date is approximate because there is no ancient record of its construction. Marcius wished to connect the newly fortified Janiculum Hill on the Etruscan side to the rest of Rome, augmenting the ferry that was there. The bridge was part of public works projects that included building a port at Ostia, at the time the location of worked salt deposits.

Ancus Marcius was the legendary fourth king of Rome, who traditionally reigned 24 years. Upon the death of the previous king, Tullus Hostilius, the Roman Senate appointed an interrex, who in turn called a session of the assembly of the people who elected the new king. Ancus is said to have ruled by waging war as Romulus did, while also promoting peace and religion as Numa Pompilius did.