Dubris, also known as Portus Dubris and Dubrae, was a port in Roman Britain on the site of present-day Dover, Kent, England.

As the closest point to continental Europe and the site of the estuary of the Dour, the site chosen for Dover was ideal for a cross-channel port. The Dour is now covered over for much of its course through the town. In the Roman era, it grew into an important military, mercantile and cross-channel harbour and — with Rutupiae (Richborough Roman fort) — one of the two starting points of the road later known as Watling Street. It was fortified and garrisoned initially by the Classis Britannica, and later by troops based in a Saxon Shore Fort.

At the start of his first attempt to conquer Britain in 55 BC Julius Caesar initially tried to land at Dubris, whose natural harbour had presumably been identified by Volusenus as a suitable landing place. However, when he came in sight of shore, the massed forces of the Britons gathered on the overlooking hills and White Cliffs of Dover dissuaded him from landing there, since the cliffs were "so close to the shore that javelins could be thrown down from" them onto anyone landing there. After waiting there at anchor "until the ninth hour" (about 3pm) waiting for his supply ships from the second port to come up and meanwhile convening a council of war, he ordered his subordinates to act on their own initiative and then sailed the fleet about seven miles along the coast to an open beach.

The Roman fleet in British waters, the Roman navy's main purpose was protecting the Gaul-to-Britain routes and supporting the land army in Britannia, not defending Britain from invasion. For this reason, its main harbor was in Gesoriacum (Boulogne), not Dover. However, it did have other, smaller bases in Britannia itself, at Rutupiae and Dubris.

Two lighthouses, each called the "Pharos", were built at Dover soon after the Roman conquest. Proposals of their date range from 50 (seven years after the invasion of 43), 80 or (since the building includes tiles identical to the mansio in the town built at that date) c. 138, though the general consensus is for a 1st-century AD date. They were sited on the two heights (Eastern Heights and Western Heights) and modelled on the Tour d'Ordre built for Caligula's aborted invasion at Boulogne.

The one on the Eastern Heights still stands in the grounds of Dover Castle to 80 feet (24 m) high close to its original height, and has been adapted for use as the bell tower of the adjacent castle church of St Mary de Castro. This Roman Pharos has been a Grade I-listed building since 1974. What little remains of the western lighthouse is called the Bredenstone or the Devil's Drop of Mortar after the putative nearby lost village of Braddon, within Drop Redoubt on Dover Western Heights — it was covered in the 18th-century building works but then rediscovered in fresh works in the 1860s, and was the traditional site of the investiture of the Lord Warden of the Cinque Ports.

At its peak, Dubris was a major trading centre, taking over from Rutupiae as the main Roman cross-Channel port. With Rutupiae, it was one of the starting points for Watling Street, the Roman road to Canterbury and, ultimately, London.

During the construction of the new A256/York Street bypass in the 1970s, Roman remains were discovered and an eight-week excavation followed. The archaeologists discovered a Roman mansio now known as the "Roman Painted House". The mansio, a hostel for government officials, was built in c. 200. It was discovered in 1970 by the Kent Archaeological Rescue Unit and, as it houses some of the finest example of Roman murals in Britain (over 400 sq ft (37 m²). of painted plaster, the most extensive ever found north of the Alps), it has been called "Britain's Buried Pompeii".