Baiae (Italian: Baia), in the Campania region of Italy on the Bay of Naples, was for several hundred years a fashionable and luxurious coastal resort, especially towards the end of the period of the Roman Republic. Baiae was even more popular than Pompeii, Naples, and Capri with the super-rich, notorious for the hedonistic temptations on offer, and for rumors of scandal and corruption.

Famous for its medicinal warm sulfur springs and purple oysters, and with a mild climate, it was an ideal retreat from heat of Rome, and many prominent Romans had villas in the area. It was at his villa near Baiae that the Emperor Hadrian died in 138 AD.

In the trial of Marcus Caelius Rufus in 60 BC, the prominent socialite Clodia was described by the defense as living the life of a harlot in Rome and in the "crowded resort of Baiae", indulging in beach parties and drinking sessions.

Seneca the Younger (who died 65 BC) wrote a moral epistle on Baiae and Vice, describing the spa town as being a "vortex of luxury" and a "harbor of vice". Things had obviously not changed much when Sextus Propertius (died 15 BC) described the town as a "den of licentiousness and vice" in one of his elegies.

Baiae was also the location for a spectacular stunt (in AD 37) by the eccentric Caligula, who on becoming Emperor ordered a temporary floating bridge to built using ships as pontoons, stretching for over two miles from the town of Baiae to the neighboring port of Puteoli, across which he proceeded to ride his horse, in defiance of an astrologer's prediction that he had "no more chance of becoming Emperor than of riding a horse across the Gulf of Baiae".