After the pivotal Battle of Pharsalus in 48 BC, Julius Caesar (Rex Harrison) emerges as the undisputed ruler of Rome after defeating Pompey's forces. At his side is his slave Flavious (George Cole). News comes from Canidius ([Andrew Faulds]), a general in Anthony's cavalry, that Pompey has escaped, presumably on his way to Egypt. Setting his sights on the land of the Pharaohs, Julius pretends to take up the role of executor for the will of the late father of the young Pharaoh Ptolemy XIII ([Richard O'Sullivan]) and his sister Cleopatra (Elizabeth Taylor).
Caught in the throes of a fierce rivalry, Ptolemy and Cleopatra are embroiled in a destructive war against one another that endangers the grain supply crucial for Rome. Julius dispatches Mark Antony back to Rome to govern in his absence, while he while traveling to Egypt with Germanicus ([Robert Stephens]), Agrippa (Andrew Keir), and Rufio (Martin Landau).
As Julius arrives in Alexandria, he encounters attempts at indignation from Ptolemy, who insists on humiliating him by forcing him to navigate through crowds to reach the palace. Not surprisingly, Ptolemy relays claims that Cleopatra aimed to kill him, leading to escalating tensions. Meanwhile, Theodotus of Chios ([Herbert Berghof]) serves as Ptolemy's advisor and Achillas ([John Doucette]), commands his personal guard.
In a playful twist of fate, Ptolemy seeks to prevent Julius from reinstating Cleopatra as co-ruler of Egypt, presenting instead the severed head of Pompey, which only angers Julius; a Roman should never be treated as such, especially by a conquered Egyptian. On her part, Cleopatra attempts to gain Julius' favor by secretly entering Alexandria and appealing for her throne, claiming her brother is in the thrall of malevolent advisors and promising a steady grain supply to Rome in exchange for her reinstatement. There’s an urgency as Cleopatra warns Julius that Ptolemy may plot against him, obtaining insights into Julius' own vulnerabilities.
Amidst this political chaos, Cleopatra employs seduction by inviting Julius to an audience during her bathing hours. In a dramatic turn of events, as Achillas mobilizes his forces to crush Julius, the Roman military leader responds by ordering the destruction of the Egyptian fleet, inadvertently causing a fire that engulfs the famed Library of Alexandria.
This incident breeds frustration between the two powerful leaders. In the height of conflict, Cleopatra holds her ground, asserting that Achillas's armies far outnumber Julius' forces. However, he successfully fends off the attack using a clever turtle formation.
Seizing control of the kingdom, Julius executes Pothinus ([Grégoire Aslan])—who had planned Cleopatra's murder—and sends Ptolemy to the eastern desert to fend for himself. Following these events, Cleopatra is crowned Queen of Egypt and nurtures grandiose dreams of ruling alongside Julius. The two eventually marry; Cleopatra persuades him of the necessity of an heir, and their son Caesarion is born, leading Julius to publicly declare him his legal heir.
However, upon returning to Rome, Julius, now dictator for life, finds unrest rising within the Senate, fueled by fears that he wishes to become a king, instigated by Cleopatra's presence. Recognizing the rising tensions, Antony warns Julius of the potential fallout and the implications of Cleopatra's ambitions.
In a shocking twist, on the Ides of March in 44 BC, a conspiracy culminates in Julius' assassination at the hands of former allies, including Brutus (Kenneth Haigh). Cleopatra, angered by Julius's will, which recognizes Octavian ([Roddy McDowall]) over her son Caesarion, flees back to Egypt amid the ensuing chaos.
As the political landscape shifts, Antony seeks Cleopatra in Egypt and becomes embroiled in a passionate affair, unsure of his footing in the fluctuating alliances. The complexities of love and power intertwine as Antony navigates alliances that leave him at the mercy of Octavian.
The rivalry culminates in the Battle of Actium, where under Agrippa's command, Octavian achieves a decisive victory over Antony's forces. In turmoil, Cleopatra devises a plan to secure her son’s future but ultimately faces betrayal from those once loyal to Antony.
As Antony spirals into despair, he succumbs to tragic circumstances, ultimately taking his life in the poignant embrace of Cleopatra. In a final act of defiance, Cleopatra chooses to end her life rather than live as a captive, committing suicide with an asp, leaving a legacy of passion, power, and tragedy. Octavian, sealed within his victory, approaches the deserted tomb too late—a haunting conclusion to an epic saga of love and ambition.
