Catiline (Lucius Sergius Catilina) (108 BC-62 BC) was a Roman politician of the 1st century BC who is best known for the Catiline (or Catilinarian) conspiracy, an attempt to overthrow the Roman Republic, and in particular the power of the aristocratic Senate.

Born from a noble but impoverished family, he served in the Social War with Pompey and Cicero, under Pompeius Strabo. He also supported Sulla in the civil war of 84-81 BC. Catiline was praetor in 68 and governed Africa in the following two years. Upon his return he was prosecuted for abuse of power, but eventually acquitted, then in 66 was accused of a conspiracy with Autronius and Sulla, although we are unclear on the details. After being defeated by Cicero in the consular election for 63, he championed the cause of aristocrats and Sullan veterans down on their luck. He also began to organize a new and larger conspiracy. Catiline made offers to various tribes in Gaul to secure allies. One tribe, the Allobroges, refused his offer and made the plot public.

In 63 BC Cicero, who was consul at the time, discovered and denounced Catiline's conspiracy to the Senate, and Catiline had to flee from Rome. He fled to Etruria. In January 62 BC he and his fellows were intercepted by the Roman army near Pistoria (now Pistoia), and he died in the subsequent battle.

Catiline's conspiracy is one of the most famous events of the Roman Republic's turbulent final decades. Cicero wrote down his orations to the Senate against Catiline, which became a widely studied example of eloquence and rhetoric; the historian Sallust wrote an account of the whole affair approximately 20 years after the fact.

The conspirators' agenda is somewhat unclear, but reportedly included arson and other property damage, the assassination of public figures (especially Cicero), and the institution of widespread debt relief or cancellation for the debtors who made up much of Catiline's support base.