A palladium or palladion is an image or other object of great antiquity on which the safety of a city or nation is said to depend. The word is a generalization from the name of the original Trojan Palladium, a wooden statue (xoanon) of Pallas Athena that Odysseus and Diomedes stole from the citadel of Troy. It was supposedly later taken to the future site of Rome by Aeneas, where it remained until perhaps transferred to Constantinople and was lost after the Empire converted to Christianity.

In Greek and Roman mythology, the Palladium or Palladion was a cult image of great antiquity on which the safety of Troy and later Rome was said to depend, the wooden statue (xoanon) of Pallas Athena that Odysseus and Diomedes stole from the citadel of Troy and which was later taken to the future site of Rome by Aeneas. The Roman story is related in Virgil's Aeneid and other works. Rome possessed an object regarded as the actual Palladium for several centuries; it was in the care of the Vestal Virgins for nearly all this time.