full name Gnaeus Pompeius Magnus (106–48 bc), Roman general and statesman, the erstwhile ally and son-in-law of Julius Caesar, but later his arch-rival for power.

Pompey was born in Rome on Sept. 29, 106 bc, into a senatorial family; his father, Gnaeus Pompeius Strabo (d. 87 bc), was consul in 89 bc. At the age of 17 Pompey fought, along with his father, on the side of Lucius Cornelius Sulla against the faction of Gaius Marius and Lucius Cornelius Cinna. In 84 bc he raised three legions and defeated the Marian party, and he was later sent to destroy the remnants of the Marian faction in Africa and Sicily. On his triumphant return to Rome he was honored with the title Magnus, or the Great. Pompey subsequently defeated the followers of Marcus Aemilius Lepidus, a one-time Sulla partisan, whom he drove out of Italy, and destroyed the Marian party in Spain (76–71 bc). Returning to Italy, Pompey brought an end to the Servile War instigated by the slave Spartacus. He was now the idol of the people and was elected consul for the year 70 bc, serving with Marcus Licinius Crassus.

In 67–66 bc, Pompey cleared the Mediterranean Sea of pirates and was subsequently given control of the provinces in the east and put in charge of the war against Mithradates VI of Pontus. Between 65 and 62 bc, Pompey conquered not only Mithradates but also Tigranes the Great, king of Armenia (c. 140–55 bc), and Antiochus XIII of Syria (r. 69–64 bc), annexing the territory of the latter to the Roman dominions. He also subdued the Jews and captured Jerusalem. On his return to Italy he disbanded his army and in 61 bc entered Rome in triumph for the third time. After his return he was anxious that his acts in Asia should be ratified by the Senate and certain lands be apportioned among his veterans. The Senate, however, declined to accede to his wishes, and Pompey, turning against the aristocratic party, now formed a close alliance with Julius Caesar, and the two men, together with Crassus, formed in 60 bc the coalition commonly called the First Triumvirate. Caesar’s daughter Julia (83?–54 bc) was given in marriage to Pompey, thus cementing their relationship. The following year Caesar repaired to Gaul, and there for nine years carried on a career of conquest while Pompey spent his time in Rome.

Jealousies, however, arose between the two leaders. Julia died in 54 bc, and Crassus was slain in Syria the following year. Pompey then returned to the aristocratic party, whose members desired to check Caesar’s ambitions and deprive him of his command. Caesar consented to the order to lay down his office and return to Rome, provided that Pompey, who had an army near Rome, would do the same. The Senate insisted on an unconditional resignation, but Caesar crossed the Rubicon in 49 bc, thus defying the Senate and its armies, which were under Pompey’s command. Pompey withdrew his forces to Brundisium (now Brindisi) and then to Greece. Caesar meanwhile made himself master of Italy and defeated a strong army in Spain, which was commanded by Pompey’s legates, and then crossed the Adriatic Sea to attack Pompey. The latter, who had gathered a strong army, was victorious at first, but was defeated at Pharsalus in 48 bc. Pompey then escaped to Egypt, where he was assassinated on Sept. 28, 48 bc.