Porto (Italian) or Portus (Latin) was a town in Lazio or Latium, just south of Rome, Italy. It was an ancient harbour on the right bank of the mouth of the Tiber.

Rome's original harbour was Ostia. Claudius constructed the first harbour on the Portus site, 4 km (2.5 mi) north of Ostia, enclosing an area of 69 hectares (170 acres), with two long curving moles projecting into the sea, and an artificial island, bearing a lighthouse, in the centre of the space between them. The foundation of this lighthouse was provided by filling one of the massive Obelisk ships, used to transport an obelisk from Egypt to adorn the spina of Vatican Circus, built during the reign of Caligula. The harbour thus opened directly to the sea on the north-west and communicated with the Tiber by a channel on the south-east. The object was to obtain protection from the prevalent south-west wind, to which the river mouth was exposed. Though Claudius, in the inscription which he caused to be erected in A.D. 46, boasted that he had freed the city of Rome from the danger of inundation, his work was only partially successful: in 62 AD Tacitus speaks of a number of grain ships sinking within the harbour during a violent storm. Nero gave the harbour the name of "Portus Augusti".

Portus Cale (Latin for Port of Cale) was the old name of an ancient town and port in current day Portugal. It was located in the north of Portugal, in the area of today's Grande Porto.

Cale was the name of an early settlement located at the mouth of the Douro River, which flows into the Atlantic Ocean in the north of what is now Portugal.

Some historians have argued that Greeks were the first to settle Cale and that the name derives from the Greek word Καλλις kallis, 'beautiful', referring to the beauty of the Douro valley. Others have hypothesized that the word Cale came from the Latin word for 'warm' (Portus Cale thus meaning Warm Port). The main explanation for the name, however, is that it is a ethnonym derived from the Castro people that settled in the area of Cale - the Callaeci or Gallaeci who named Gallaecia (which included Northern Portugal). In 1864 Hector Boece said Portugal derived from Porto Gatelli the name Gatelo gave to Braga when he settled there while others say he gave that name to Porto. The names "Callaici" and "Cale" are the origin of today's: Gaia, Galicia, and the "Gal" root in "Portugal". The meaning of Cale or "Calle" is however not fully understood.