The First Triumvirate was the political alliance of Gaius Julius Caesar, Marcus Licinius Crassus, and Gnaeus Pompeius Magnus. Unlike the Second Triumvirate, the First Triumvirate had no official status whatsoever; its overwhelming power in the Roman Republic was strictly unofficial influence, and was in fact kept secret for some time as part of the political machinations of the Triumvirs themselves. It was formed in 59 BC and lasted until Crassus' death in 53 BC.

Crassus and Pompey had been colleagues in the consulship in 70 BC, when they had legislated the full restoration of the tribunate of the people (the dictator Lucius Cornelius Sulla had stripped the office of all its rights except the ius auxiliandi, the right to rescue a plebeian from the clutches of a patrician magistrate). However, since that time, the two men had entertained considerable antipathy for one another, each believing the other to have gone out of his way to increase his own reputation at his colleague's expense.

Caesar contrived to reconcile the two men, and then combined their clout with his own to have himself elected consul in 59 BC; he and Crassus were already friends (modern consensus as to the beginning of the friendship to be as early as 65 where a young Caesar supported Crassus's proposal to make Egypt tributary to Rome), and he solidified his alliance with Pompey by giving him his own daughter, Julia, in marriage. The alliance combined Caesar's enormous popularity and legal reputation with Crassus's fantastic wealth and influence within the plutocratic Equestrian order (ordo equester) and Pompey's equally spectacular wealth and military reputation.