in ancient Rome:
(1) A board of three persons appointed or elected for a specific purpose, for example, the triumvirate created to administer the agrarian reforms of Tiberius Gracchus in 133 B.C.
(2) During the civil wars of the first century B.C., an alliance formed by influential political figures and generals with a view to seizing power. The First Triumvirate (60 or 59 B.C.) was an alliance between Caesar, Pompey, and Crassus, in which Caesar played the leading role and support came from the legions. Having assumed the powers of government, the members of the First Triumvirate distributed governmental posts in Rome and the provinces among themselves and their supporters and instituted laws in their own behalf. The death of Crassus in 53 B.C. and strained relations between Pompey and Caesar brought about the dissolution of the First Triumvirate, which Varro had called “the three-headed monster.”
The Second Triumvirate was an alliance lasting from 43 to 36 B.C. and existing in name until 31 B.C. The Caesarians Octavian, Antony, and Lepidus joined together against Caesar’s murderers—Brutus and Cassius—as well as other republicans and the Senate. Unlike the First Triumvirate, the second had the support of the comitia, which granted the triumvirs extraordinary powers to “settle the Constitution.” The triumvirs used this power to divide the provinces among themselves and to publish proscriptiones against political adversaries. The Second Triumvirate was dissolved because of internal dissension, primarily between Octavian and Antony.