The famous leader who crossed the Rubicon in 49 B.C., igniting a civil war in Rome, was Julius Caesar. His crossing of the Rubicon River symbolized a decisive act of rebellion against the Roman Senate's authority, essentially declaring war. This audacious move resulted in a series of military campaigns and political maneuvers that led to Caesar's rise to power and the eventual end of the Roman Republic. His actions and the subsequent civil war changed the course of Roman history, ultimately leading to the establishment of the Roman Empire under his adopted heir, Augustus.