In Julius Caesar's will, his grand-nephew, Octavius, was named as his heir and adoptive son. Octavius was related to Caesar through his grandfather, who married a sister of the Roman dictator.
As one of the three triumvirs, Octavius is the youngest and the most ambitious of the three. He began his career with little — except the name of his grand-uncle Julius Caesar, his father by adoption, and he naturally wanted more — all that was possible. Having been named heir in Caesar's will, Octavius comes to Rome to claim his fortune.
Nothing exists for young Caesar except the single goal of acquiring and maintaining power. As such, he is the antithesis of Antony, who becomes involved in a love affair that ultimately outweighs his own quest for mastery of the world. Because of the limited range of Octavius's vision and interests, he often appears cold and calculating, and many of his actions are indeed calculated ones. In betrothing his beloved sister to Antony, his long-time rival, he shows that he is capable of placing political expediency above family loyalty. Conversely, when Antony abandons Octavia, Octavius acts like the outraged brother who wishes to avenge his sister's honor. While his pride is understandably piqued, his anger also hints of opportunism, for here is the perfect pretext for attacking his rival.
Octavius struggles for supremacy within the Triumvirate, but interestingly, his contest is only with Antony, for neither he nor Antony considers Lepidus an equal. Throughout the drama, neither Antony nor Octavius trusts the other. Nor does Octavius's sister, Octavia, wholly trust Antony. She is well aware of his greater experience in battle and statesmanship, as well as his popularity with his soldiers and with the public, compared to her brother's inexperience. Quite naturally, Octavius is insecure about his ability to succeed in an arena where Antony has been active for close to twenty years. But he gains confidence as he observes Antony's dissipated life in Egypt, and he takes advantage of every situation he can.
Octavius has few devoted friends, and Shakespeare seemingly uses him to illustrate the lot of the ruler who must sacrifice everything to stay in power. He trusts no one, and he fears to let himself be close to few, if any, of his men. His treatment of Lepidus is one example of how he can cast aside presumed friends in order to achieve even more power. It is possible, of course, that Antony might have treated Lepidus unfairly, but in fact, it was Octavius who imprisoned the third member of the Triumvirate and confiscated his lands. Octavius, at times, seems almost without principle. For example, one of Octavius's closest friends, his officer Dolabella, surreptitiously helps Cleopatra by warning her that Octavius plans to take her to Rome in disgrace if she is captured. Cleopatra is thus able to thwart Octavius's devious schemes. She takes her own life and thus deprives him of parading her through the streets of Rome in disgrace — all for the glory of Octavius, the conqueror. Basically, then, we can say that Octavius symbolizes the world of power, politics, and war. The Rome of this play is the Rome of the waning Republic. It is a masculine, taciturn, and seemingly pleasureless place: fittingly, it is the seat of Octavius's realm.
While Octavius's character often seems pale in comparison with Shakespeare's portraits of Antony and Cleopatra, he is vital to the play, for he functions both as Antony's antagonist and as his foil. Without the dour young Octavius as a rival and as a contrast, Antony's virtues, as well as his faults, would not be so vividly apparent for the audience — nor for Cleopatra, for that matter.