Tarquinius (plural Tarquinii; compare the place name Tarquinia) is the gens name (nomen) of a Roman family of Greco-Etruscan origin. Two Tarquins were among the semi-legendary kings of Rome.
The Tarquinii appear only in the legendary accounts of the pre-republic Roman Kingdom. The presence of two King Tarquins in the legend, the second being ousted as a tyrant, may indicate that a family by that name attempted to monopolize political power beyond what Roman custom and tradition considered acceptable at the time. According to tradition, the precipitating event was the rape of Lucretia by Sextus Tarquinius, the king's son. The expulsion of the Tarquins signaled the end of the Regal period and the beginning of the Republic in Roman history.