The Portland Vase is a first-century Roman glass vase, which served as an inspiration to many glass and porcelain makers from about the beginning of the 18th century onwards. Since 1945 the vase has belonged to the British Museum.

The vase is about 25 centimetres high and 56 in circumference. It is made of violet-blue glass, and surrounded with a single continuous white glass cameo depicting seven figures (humans and gods). Though still mysterious, one interpretation is that the figures depict two different scenes, one the story of the Emperor Augustus' supposed siring by the god Apollo, and the other a divinatory dream by Hecuba that the Judgement of Paris would lead to the destruction of Troy. Another interpretation of the first scene is that it is Peleus and Thetis. On the bottom is a head, presumed to be of Paris on the basis of the Phrygian cap it wears. Based on the scenes and the style of the work, the Portland Vase is believed to have been made in Alexandria some time between 20 BC and the year 100.

Legend has it that it was discovered in the sepulchre of the Emperor Alexander Severus near Rome some time around 1580, but the first possible historical reference to the vase is in a 1601 letter from the French scholar Nicolas Claude Fabri de Peiresc to the painter Peter Paul Rubens. Another story says that it was found in a sarcophagus excavated at Monte del Grano (also near Rome) some time between 1623 and 1644. After being owned by the Barberini family for some two hundred years, it was then purchased by Sir William Hamilton and brought to England.

From there it ended up in the possession of William Cavendish-Bentinck, 3rd Duke of Portland and at times the Prime Minister of the United Kingdom. After a friend broke the base of it, he loaned the vase to the British Museum for safe-keeping, at which point it was dubbed the "Portland Vase."

In 1845, the vase was accidentally shattered to pieces by one William Mulcahy, who had drunkenly leaned on the case. The vase was pieced together, with mild success, but after the Duke's descendants sold the vase to the museum in 1945, a second and better reconstruction was done. The third and current reconstruction took place in 1986, and managed to reincorporate several small stubborn pieces that had been saved for more than 140 years. Little sign of the original damage is visible now.

From the standpoint of art history the vase is interesting as it twice served as a major source of artistic inspiration in two favorite British media. Josiah Wedgwood devoted considerable time at the end of the 18th century to duplicating it in porcelain, then in the 19th century a £1000 prize was offered by Benjamin Richardson to anyone who could duplicate the cameo work in glass. The latter work proved to be incredibly painstaking, and based on this it is believed that the Portland Vase must have taken its original artisan no less than two years to produce.