The son of Egerius, who was the son of Aruns, the brother of Tarquinius Priscus. When the town of Collatia was taken by Tarquinius Priscus, Egerius was left in command of the place (Liv. i. 38), and there his son also resided, whence he received the surname of Collatinus. He was married to Lucretia, and it was the rape of the latter by his cousin, Sex. Tarquinius, that led to the dethronement of Tarquinius Superbus, and the establishment of the republic, b. c. 509. Collatinus and L. Junius Brutus were the first consuls; but as the people could not endure the rule of any of the hated race of the Tarquins, Collatinus was persuaded by his colleague and the other nobles to resign his office and retire from Rome. He withdrew with all his property to Lavinium, and P. Valerius Poplicola was elected in his place. (Liv. i. 57-60, ii. 2 ; Dionys. iv. 64, &c.; Dion Cass. Frag. 24, ed. Reimar; Cic. de Rep. ii. 25, de Off. iii. 10.)