Trebonius, Caius (trēbōˈnēəs) [key], d. 43 B.C., Roman politician. When tribune (55 B.C.) of the plebs he proposed the Lex Trebonia by which Pompey obtained Spain, Crassus obtained Syria, and Caesar obtained Gaul and Illyricum. As Caesar's protégé he became praetor (48 B.C.), propraetor in Spain (47), and consul (45). Notwithstanding the promise by Caesar of the province of Asia, he was a leading conspirator against his patron. He was slain in Smyrna by Dolabella.