wealthy naturalized Roman, important in Roman politics in the last years of the republic.

In 72 BC Pompey the Great conferred Roman citizenship on Balbus and his family for his services against the rebel Quintus Sertorius (Sertorius, Quintus) in Spain. Balbus became friends with several prominent politicians; in Rome he played a part in the formation of the alliance in 60 between Julius Caesar (Caesar, Julius), Pompey, and Marcus Crassus (Crassus, Marcus Licinius).

Balbus had impressed Caesar, who in 62 appointed him chief of staff in his praetorship. This appointment may have continued into Caesar's proconsulate in Spain (61–60). Balbus held the position again when Caesar was consul in Rome in 59. During Caesar's years as proconsul in Gaul (58–50), Balbus helped watch over his interests in Rome. In 56 Balbus was prosecuted for the alleged illegality of his naturalization (an attack aimed chiefly at the three dynasts, Caesar, Pompey, and Crassus). Pompey, Crassus, and Cicero (Cicero, Marcus Tullius) defended Balbus, and he was acquitted. In 50–49 he tried to prevent the outbreak of civil war, and later he attempted to mediate between his friends Caesar and Pompey; for these actions he hoped to gain Cicero's support.

Balbus refused to fight against Pompey, but he became Caesar's chief agent in Rome, thus adding to his immense fortune. He helped Cicero in his political and economic difficulties and remained his friend by judicious flattery.

In 44 he met Octavian (the future Augustus) on his arrival in Italy and introduced him to Cicero, then supported him throughout the Civil Wars. Probably praetor after Caesar's death, in 40 he became the first naturalized Roman to hold a consulship. He died after 32 BC, leaving 25 denarii to every citizen.

His nephew of the same name (sometimes called Lucius Cornelius Balbus Minor 【“the Younger”】 to distinguish them) remained a friend of Augustus. Balbus Minor was the first naturalized Roman—and the last man not related to an emperor—to celebrate a triumph (19 BC).