Marcus Tullius Cicero is best known as Rome's greatest orator and as a man of letters. Cicero, also known as Tully, was born in Arpinum (now Arpino, Italy). As a youth he studied law, oratory, literature, and philosophy in Rome. After brief military service and three years' experience as a lawyer defending private citizens, he traveled to Greece and Asia, where he continued his studies. He returned to Rome in 77 BC and began his political career. In 74 BC he was elected to the Senate.

Although Cicero's family did not belong to the Roman aristocracy, he was supported in the competition for the consulship in 64 BC by most rich and powerful Romans because of their distrust of his aristocratic but less respectable rival, Lucius Sergius Catilina, known as Catiline. Cicero was elected, but during his administration Catiline organized a plot to overthrow the government. Cicero suppressed the conspiracy and had several members of Catiline's group executed. Julius Caesar and other Roman senators argued that Cicero had acted too hastily, without giving the conspirators due process of law. As a result, in 58 BC, Cicero was forced into exile. After a year in Macedonia he was recalled by the Roman general Pompey the Great.

Cicero occupied himself with literature until 51 BC, when he accepted an assignment to govern the Roman province of Cilicia as proconsul. He returned to Rome in 50 BC and joined Pompey, who had become Caesar's bitter enemy. After Pompey was defeated by Caesar in 48 BC, Cicero, realizing that further resistance was hopeless, accepted Caesar's overtures of amity. While Caesar was virtual dictator of Rome, Cicero lived as a private citizen and wrote extensively. After Caesar's assassination in 44 BC, Cicero returned to politics. Hoping to see a restoration of the Republic, he supported Caesar's adopted son Octavian, who later became the emperor Augustus, in a power struggle with the Roman consul Mark Antony. Octavian and Antony were reconciled, however, and Cicero was executed as an enemy of the state on Dec. 7, 43 BC.

Cicero created a rich prose style that combines clarity with eloquence and has become one of the standards by which all other Latin prose is judged. He greatly enriched the vocabulary of his own language. Cicero's writing covers numerous subjects of intellectual interest. Nearly all of his philosophical works were borrowed from Greek sources and, apart from an intrinsic merit, are of great value in preserving much of Greek philosophy that might otherwise have remained unknown. Outstanding are the treatises On the Republic, On the Laws, On Duty, and On the Nature of the Gods. His rhetorical works, written in dialogue form, particularly On the Orator, are of value as the products of an accomplished rhetorician and as a rich source of historical material. The most famous of his orations are the 4 against Catiline and the 14 so-called Philippics against Antony.

Among the minor works of Cicero, the treatises On Old Age and On Friendship have always been admired for their urbane, cultivated style. Highly important are four collections of letters written by Cicero to acquaintances and friends. These letters are a spontaneous self-revelation of their author and an excellent source of information on the politics and customs of ancient Rome.