Baiae (in modern Italian Baia), a frazione of the comune of Bacoli in the Campania region of Italy, was a Roman seaside resort on the Bay of Naples. It was said to have been named after Baius, who was supposedly buried there. Baiae was for several hundred years a fashionable resort, especially towards the end of the Roman Republic. Baiae was even more popular than Pompeii, Herculaneum, and Capri with the super-rich, notorious for the hedonistic temptations on offer, and for rumours of scandal and corruption. Baiae was an integral part of Portus Julius, home port of the western Imperial Fleet of ancient Rome.
Baiae was sacked by Muslim raiders in the 8th century AD and was deserted because of malaria by 1500. Because of coastal subsidence most of Baiae is now under water in the Bay of Naples, largely due to local volcanic activity.