The Optimates ("Best Men", singular optimas; also known as boni, "Good Men") were the traditionalist majority of the late Roman Republic. They wished to limit the power of the popular assemblies and the Tribunes of the Plebs, and to extend the power of the Senate, which was viewed as more dedicated to the interests of the aristocrats who held the reins of power. In particular, they were concerned with the rise of individual generals who, backed by the tribunate, the assemblies and their own soldiers, could shift power from the Senate and aristocracy. They were opposed by the populares. It is also important to note that many members of this faction were so classified because they used the backing of the aristocracy and the senate to achieve personal goals, not necessarily because they favored the aristocracy over the lower classes. Similarly, the populares did not necessarily champion the lower classes, but often used their support to achieve personal goals.
The optimates favored the nobiles (noble families) and opposed the ascension of novi homines ("new men", usually provincials) into Roman politics. Cicero, a strong supporter of the optimates' cause, was himself a novus homo, being the first in his family to enter the Senate, and was never fully accepted by the optimates. During the Civil War of 49BC, Julius Caesar, of a respectable old family, contended against a Senate championed by Pompey the Great, a new man.
In addition to their political aims, the optimates opposed the extension of Roman citizenship, and sought the preservation of the mos maiorum, the ways of their forefathers. They sought to prevent successful generals, such as Gaius Marius, Pompey the Great, and Julius Caesar, from using their armies to accrue such power that they might be in a position to challenge the Senate. They opposed Marius' plan to enlist impoverished Romans, too poor to provide their own arms and supplies in the legions, and the generals' attempts to settle these veterans on state-owned land.
The optimates' cause reached its peak under the dictatorship of Lucius Cornelius Sulla (81 BC–79 BC). During his reign, the Assemblies were stripped of nearly all power, the Senate membership was raised from 300 to 600, thousands of soldiers were settled in northern Italy, and an equally large number of populares were executed via proscription lists. However, after Sulla's resignation and subsequent death, many of their policies were gradually reversed.
Besides Sulla, notable optimates included Lucius Licinius Lucullus, Cato the Younger, Titus Annius Milo, Marcus Calpurnius Bibulus and Marcus Junius Brutus. Though they had opposed him for the entirety of his political career, Pompey the Great also found himself as the leader of the optimates' faction, once their civil war with Julius Caesar began. Optimates, along with disillusioned populares, who had carried out Caesar's assassination called themselves Liberatores.