Tribune was the title given to three separate offices during the Roman Republic: the Tribune with Consular Power, an office of the fifth and fourth centuries B.C., obsolete by the time of the Third Servile War; the military and tribune, officers ranking between the centurions and the legate commanding each legion; and the Tribune of the Plebians, the most powerful office of the Roman Republic, although most of its powers were negative, blocking affimative actions by the magistrates or the Senate.
The Tribunes of the Plebians were the champions of the plebian class, elected by the Committee of the Plebians, identical in organisation to the Committee of the Tribes, but consisting only of the plebians of each tribe. The Committee of the Plebians elected ten Tribunes of the Plebians to intercede against the acts of the Senate and the magistrates. The person of a Tribune of the Plebians was sancrosanct, protected from any assault or indignity, and could extend this inviolability in the form of a veto against any act of the Senate or magistrates. This power to paralyze the government amounted to a greater power than wielded positively by the Senate and magistrates, and the Tribunes of the Plebians were regarded as the most powerful political figures of the Roman Republic.