- 1: the laboring class; especially : the class of industrial workers who lack their own means of production and hence sell their labor to live
- 2: the lowest social or economic class of a community
The proletarii according to the Constitution of the Roman Republic were men without property. The proletarii were also called capite censi because they were "persons registered not as to their property which was below the lowest census for military service, but simply as to their existence as living individuals, primarily as heads (caput) of a family."
The Comitia Centuriata was an people's assembly of early Rome composed of centuriae (nominally, groups of about 100 men) who were classified according to the value of each one's property. It met on the Campus Martius. Yet this assembly was already obsolete in the last centuries of the Republic (509-44 B.C.) and had become ill-understood. Latter Roman historians, e.g., Livy, not without some uncertainty, understood the Comitia Centuriata as a means of designating military duties demanded and voting rights granted, according to wealth. A favored reconstruction of this assembly has 18 centuries of calvary, and 170 centuries of infantry divided into five classes by wealth, plus 5 centuries of support personnel. The top infantry class assembled with full arms and armor; the next two classes brought arms and armor, but less and lesser; the fourth class only spears; the fifth slings. In voting the calvary and top infantry class were enough to decide an issue; as voting started at the top, an issue might be decided before the lower classes voted. The membership of these five classes were called adsidui. Excluded were the proletarii, those who did not qualify for any of these five classes because "they had not even the minimum property required for the lowest class. Their sole possession was their children, proles; hence the name. The proletarii were the poorest stratum of the population." One of the five support centuries, however, possibly was composed of proletarii (who were usually free of military service, except in the case of emergencies).
In time the number of Roman family farmers became significantly reduced, perhaps due to overreaching or corruption by the Senate oligarchy following the Second Punic War (218-201). As a result there were not enough people whose property qualified them to perform the citizenry's military duty to Rome. The Roman general Gaius Marius (157-86), a plebian originally sprung from poor rural roots, in 107 first introduced the widespread use of proletarii in the Roman Army, which action was known as the Marian reforms.