Julius Caesar takes place during 44 and 42 BCE. These years mark the final moments of the Roman Republic, and the beginning of the civil war that resulted in the creation of the Roman Empire. The first four acts of the play take place in the city of Rome, while the final act is set in and around a Roman-controlled battlefield in Greece. During this period Rome consisted of an urban center, in the city of Rome itself, and a large collection of client-states around the Mediterranean Sea. Though the relationship between these populations was complex, most Roman citizens saw themselves as the superior conquerors, and the other parts of the empire as the inferior conquered peoples. This civic sense of superiority was reflected in the fact that taxes from all throughout the Republic made their way to the city of Rome for the benefit of the rulers and, to a lesser extent, the Roman citizens.

More important than the geographical setting of the story is its political setting. Shakespeare sets Julius Caesar during a period of great political conflict in the Roman Republic. For nearly 500 years the Republic had been ruled by a group of senators and a pair of consuls drawn from the wealthiest and most powerful families of Rome. However, throughout the history of the Republic, wars had been fought with enemies both external and internal, including a series of civil conflicts that occurred immediately before the events of the play. During these conflicts, Julius Caesar defeated Pompey and managed to amass the most personal and political power of any Roman citizen. Caesar had been awarded the position of Consul, or dictator, for life—an unprecedented title that gave him unlimited power. Romans grew concerned that Caesar had too much power in his hands, and that his monarchic rule directly contradicted the goals of the Republic. As the play dramatizes, these Roman citizens became convinced that the only way to stop Caesar would be to assassinate him, which they did on March 15, 44 BCE.