The Capitolium or Capitoline Hill ( KAP-it-ə-lyne, kə-PIT-; Italian: Campidoglio [kampiˈdɔʎʎo]; Latin: Mons Capitolinus [ˈmõːs kapɪtoːˈliːnʊs]), between the Forum and the Campus Martius, is one of the Seven Hills of Rome.

The hill was earlier known as Mons Saturnius, dedicated to the god Saturn. The word Capitolium first meant the temple of Jupiter Optimus Maximus later built here, and afterwards it was used for the whole hill (and even other temples of Jupiter on other hills), thus Mons Capitolinus (the adjective noun of Capitolium). In an etymological myth, ancient sources connect the name to caput ("head", "summit") and the tale was that, when laying the foundations for the temple, the head of a man was found, some sources even saying it was the head of some Tolus or Olus. The Capitolium was regarded by the Romans as indestructible, and was adopted as a symbol of eternity.

By the 16th century, Capitolinus had become Capitolino in Italian, and Capitolium Campidoglio. The Capitoline Hill contains few ancient ground-level ruins, as they are almost entirely covered up by Medieval and Renaissance palazzi (now housing the Capitoline Museums) that surround a piazza, an urban plan designed by Michelangelo.

The word Capitolium still lives in the English word capitol, and Capitol Hill in Washington, D.C. is widely assumed to be named after the Capitoline Hill.