censor, in ancient Rome, a magistrate whose original functions of registering citizens and their property were greatly expanded to include supervision of senatorial rolls and moral conduct. Censors also assessed property for taxation and contracts, penalized moral offenders by removing their public rights, such as voting and tribe membership, and presided at the lustrum ceremonies of purification at the close of each census. The censorship was instituted in 443 bc and discontinued in 22 bc, when the emperors assumed censorial powers.
The censors, who always numbered two, were elected normally at five-year intervals in the Comitia Centuriata (one of the assemblies in which the Roman people voted). Plebeians became eligible in 351 bc for the originally patrician office. Judgments were passed only with the agreement of both incumbents, and the death or abdication of one resulted in the retirement of the other.