Lucius Junius Brutus was the founder of the Roman Republic and traditionally one of the first Consuls in 509 BC.

Prior to his accession, Rome had been ruled by kings. Brutus led the revolt that overthrew the last king, Lucius Tarquinius Superbus, on account of Tarquin's son (Sextus Tarquinius) raping Brutus' kinswoman Lucretia. The account is from Livy's Ab Urbe Condita and deals with a point in the history of Rome prior to reliable historical records (virtually all prior records were destroyed by the Gauls when they sacked Rome in 390 BC). According to Livy, Brutus had a number of grievances against the king, amongst them was the fact that Tarquin had orchestrated the murder of his brother who was a powerful senator, opposed to Tarquin's assumption of the throne.

Brutus then infiltrated Tarquin's family by impersonating a dullard (in Latin brutus translates to dullard). He accompanied Tarquin's sons on a trip to the Oracle of Delphi. The sons asked the oracle who would be the next ruler of Rome. The Oracle responded the next person to kiss his mother would become king. Brutus interpreted mother to mean the Earth, so he pretended to trip and kissed the ground. Upon returning to Rome, Brutus was forced to fight in one of Rome's unending wars with the neighboring tribes. Brutus returned to the city when he found out about the rape of Lucretia. Lucretia, believing that she was dishonored killed herself. This event proved to be the straw that broke the camel's back. Brutus then instigated a popular uprising against the monarchy, forcing Tarquin to return home. When Tarquin arrived at Rome, he and his family were exiled, and Brutus declared power to be in the hands of the Senate.

There is some confusion as to the details of Brutus' life. His consulship, for example, may have been a later embellishment to give the republican institutions greater legitimacy by associating them with the overthrower of the kings. Similarly the tale of Brutus' execution of his own sons for failing in their military duties may well have been a later invention. His consulship came to an end during a battle with the Etruscans, who had allied themselves with the Tarquins to restore them to power in Rome.

He was said to have served his consulship along with Lucretia's widowed husband.