Decemviri (singular decemvir) is a Latin term meaning "Ten Men" which designates any such commission in the Roman Republic (cf. Triumviri, Three Men). Different types of decemvirate include the writing of laws with consular imperium (legibvs scribvndis consvlari imperio), the judging of litigation (stlitibvs ivdicandis), the making of sacrifices (sacris facivndis), and the distribution of public lands (agris dandis adsignandis).

In 452 BC the plebeians and patricians of Rome agreed to the appointment of a commission of ten men to write up a code of law defining the principles of Roman administration; during the decemviri's term in office, all other magistracies would be suspended, and their decisions were not subject to appeal. The first set of decemviri, composed entirely of patricians, assumed office in 451 BC, and was led by Appius Claudius Crassus and Titus Genucius Augurinus, who were consuls for that year. Each decemvir administered the government for one day in turn, and whichever decemvir presided on any given day was preceded by the twelve lictors bearing the fasces; none of the other decemviri received any protection from the lictors. Their administration of justice was exemplary and they submitted to the Comitia Centuriata a code of laws in ten headings, which was passed.