The Roman general who crossed the Rubicon River, igniting a civil war, is Julius Caesar. In 49 BCE, his decision to lead his army across the Rubicon was a direct challenge to the Roman Senate, marking a pivotal moment in Roman history. This act signified defiance against authority and sparked a series of events leading to a civil war, ultimately resulting in Caesar declaring himself dictator and paving the way for the end of the Roman Republic. His crossing of the Rubicon became a metaphor for committing to a risky and irreversible decision.