The Senate now names Caesar Dictator Perpetuus, "dictator for life" or "perpetual dictator".

Roman mints print a denarius coin with this title and his profile on one side, and with an image of the goddess Ceres and Caesar's title of Augur Pontifex Maximus on the reverse.

Caesar, who is apparently moving toward a monarchical system, is also awarded tribunician sacrosanctity.

Around this time, many senators began to fear Caesar's growing power.

Many of those he had earlier pardoned, fearing that he will make himself an absolute king, conspire to assassinate him.

Gaius Cassius Longinus, reconciled to Caesar, becomes praetor peregrinus and is promised the governorship of Syria for the following year.

The appointment of his junior, Brutus, as praetor urbanus deeply offends him, and he becomes one of the busiest conspirators.

Brutus, pressured into joining the conspiracy by the other senators, also discovers messages written on the busts of his ancestors.

Apparently a sincere patriot (within the confines of the aristocratic republican tradition) who hopes—naively—for the restoration of the free republic without further violence, Brutus scrupulously opposes the assassination of anyone except Caesar.

Cassius argues for the killing of Lepidus and Antony as well, but Brutus overrules him, saying the action is an execution not a political coup.

Cassius and Brutus lead some sixty conspirators—former friends and old enemies, honorable patriots and men with grievances—in stabbing Caesar to death at a meeting of the Senate in Pompey's theater on March 15 (the Ides of March), 44 BCE.

Cleopatra behaves with a discretion that she is later to discard, and her presence seems to have occasioned little comment; officially, she is negotiating a treaty of alliance.

The Optimate orator Marcus Tullius Cicero, uninvolved in the plot against Caesar, mentions her in none of his contemporary letters, though his later references to her show that he regarded her with rancor, as did most Romans.

Brutus and Cassius, referring to themselves and their fellow conspirators as “Liberators,” expect all Romans to rejoice with them in the rebirth of “freedom.”

To the Roman people, however, the freedom of the governing class is a non-issue; the armies (especially in the west) had been attached to Caesar; and the Senate is full of Caesarians at all levels, cowed but biding their time.

The Roman middle and lower classes, with whom Caesar had been immensely popular, and had been since Gaul and before, are enraged that a small group of aristocrats has killed their champion.

Antony, the surviving consul, whom Brutus had been too scrupulous to murder with his patron, had escaped Rome dressed as a slave, fearing that the dictator's assassination would be the start of a bloodbath among his supporters.

When this does not occur, he soon returns to Rome, discussing a truce with the assassins' faction.

Following a speech by Cicero in the Senate, an amnesty is agreed for the assassins on March 17.

Antony delivers an "inflammatory" eulogy at Caesar's funeral, mounting public opinion against the assassins.