|First appearance||The Stolen Eagle|
|Last appearance||De Patre Vostro (About Your Father)|
Servilia (Former Lover, deceased)
Caesar (Great-Uncle, deceased)
Mark Antony (Ex-husband, deceased)
Glabius (Ex-husband, deceased)
Agrippa (Lover/Son in law)
Drusus (Son in law)
Octavia is the daughter of Atia, sister of Octavian, and great-niece of Julius Caesar. She is later wed to Mark Antony.
At the start of the series, Octavia behaves like a typical teenage girl. She is whiny, bratty, and cries at the slightest provocation. However, as the series progresses, Octavia becomes significantly more mature and powerful in her own way, though she never matches the deviousness of her mother, Atia.
Born to one of the most powerful families in Rome, the Julii, Octavia is the only daughter and elder child of Atia of the Julii, the niece of Gaius Julius Caesar. Octavia, alongside her mother, raised her younger brother Gaius Octavian, with whom she has a fairly strong relationship. She was originally in an arranged marriage with Glabius, and despite difficulties they grew to love each other. However, upon the death of their cousin Julia, Atia is asked by Caesar to find another girl in their family to marry Pompey Magnus. Atia forced Octavia and Glabius to get a divorce. Octavia is then offered up for pre-marital relations with Pompey by Atia, which he accepts. However, he rejects the marriage for another woman called Cornelia following Pompey's attempt to turn the people and the Legio XIII Gemina against Caesar by stealing their standard and kidnapping Octavian in the process.
Octavia continues to visit her ex-husband behind her mother's back until Atia decides to deal with it by killing him and blaming it on the fact that many nobles allied with the Julii have been killed. While Octavia suspects her mother, she lets it rest when her brother assures her that it is unlikely. Following Caesar's defeat in Greece, Atia sends Octavia to ask help from Servilia, Caesar's ex-lover, who at first appears to feel sorry for Octavia being used by her mother in such a way. When Servilia receives news that Caesar has won and Servilia fears that her son Brutus is dead, Octavia shows her pity and they end up becoming lovers.
Upon Caesar's return to Rome and Octavian's return from school, Octavia casually slips that Octavian may have been Caesar's lover in his youth but denied it saying that Caesar had a "serious affliction". Upon hearing this, Servilia insists that Octavia find out what this affliction is, even if it means seducing Octavian. Upon being told by Servilia that Atia killed Glabius, Octavia does as she says and seduces Octavian in trying to find out what the affliction is. However, Octavian still refuses to tell her and when Atia finds out about Octavia and Servilia, she attempts to beat Octavia for being weak-minded and foolish.
Ashamed of herself, Octavia sends herself into self-imposed exile but is brought back to Rome by Octavian who is sent by Atia to bring her home. Following her events with Servilia, Octavia appears to have learnt her lesson as reveals in the last episode of the season that she is above petty affections, or at least tries to be.
Servilia utilizes secret information about Lucius Vorenus, which Octavia shared with her in confidence, to help plan the murder of Caesar. Octavia curses her as a result and admits to her brother that she feels guilty for the part she played in the death of her uncle. After Octavian is named Caesar's heir, he tries to tell her about his plan to gain power and save the Republic, only to have her laugh in his face. A few months later, after he has left home to raise an army, his friend Marcus Agrippa arrives to deliver a message. In a conversation with him Octavia claims to have written her brother several times in the hopes of convincing him to stop "this nonsense", but that he never listens to her. Agrippa, who is clearly attracted to her, tells her that she has more influence over her brother than she thinks.
Agrippa stumbles upon a hemp-addled Octavia at an orgy with her friend Jocasta in Heroes of the Republic, and carries her unwillingly home. Atia berates her daughter, scandalised by her behaviour; she thinks it will arouse Octavian's ire, and threatens Agrippa to keep quiet. He insists he would never do anything to hurt Octavia and alludes to the high esteem he feels for her, adding the admonition to Atia that she never speak to Octavia that way in his presence again.
In the episode Philippi, Agrippa admits to Octavia that he loves her, nonetheless aware that it is hopeless for him to think a common man like him could ever marry the sister of Octavian. She insists she will be with whom she wants, but Agrippa notes, "No ... you'll marry some useful nobleman of your brother's choosing." Later, they become lovers and share a few passionate hours before Agrippa must leave with Octavian and Antony for Greece to fight Brutus and Cassius. Octavia ignores Agrippa as she says goodbye to her brother, but Atia knows immediately that they are romantically involved.
In Death Mask, Atia suggests that the marriage between her and longtime lover Mark Antony finally occur as a show of unity between Antony and Octavian. The men agree that such an arrangement is necessary, but to Atia's surprise it is Octavia who is betrothed to Antony. Understanding that Octavia's childbearing age makes her more suitable for the match, Atia goes along with the marriage – but is furious. Later, Octavia accepts Antony's advances in bed, resigning herself to her role as his wife.
Octavian's darker side emerges further in A Necessary Fiction as he discovers that not only is Octavia is involved with Agrippa, but Atia and Antony have resumed their affair. Furious, Octavian commands Antony to leave Rome indefinitely, or be publicly shamed with Octavia's adultery. He sends Atia and Octavia into seclusion (under armed guard) at Atia's villa, and solemnly forgives a shamed and remorseful Agrippa. Atia later manages to sneak Agrippa into the house as a surprise for Octavia, but he brings bad news; despite her pleas for them to run away together, an honourable Agrippa has decided to break off the relationship out of respect for Octavian. Octavia accuses him of choosing the power Octavian gives him over her, and calls him a coward. As she walks away, Octavia mentions that she is pregnant; to whether the father is Agrippa or Anthony, she says, "Who knows? Neither man is worth a brass obol, so what matter?"
Years later in the next episode, Deus Impeditio Esuritori Nullus, Octavia is living with Atia in Rome, raising her blonde daughter Antonia alone. Mark Antony is in Egypt with Cleopatra and their own twins, Helios and Selene; when he refuses Octavian's request for increased grain supplies for a starving Rome, Octavian sends his mother and sister to intervene. Trying to avoid Cleopatra's jealous fury (and prevent Atia's public humiliation or murder), he has his wife and former lover sent away without seeing them. Atia is devastated, and an offended Octavia tosses her wedding ring into the sea. In the series finale, De Patre Vostro (About Your Father), Octavia takes the death of her husband matter-of-factly. Octavian asks Octavia to raise Antony and Cleopatra's twins, and she accepts. At Octavian's triumph, she is seen catching the glance of Agrippa.
- The historical Octavia Minor's first husband was Gaius Claudius Marcellus Minor, and she bore him three children, Marcellus, Claudia Marcella Major and Claudia Marcella Minor; the Octavia in the series is married to a nobleman named Glabius, with whom she has no children.
- In reality, it was Caesar who wanted her to marry Pompey, not Atia, and Octavia was widowed four years after Caesar's assassination, not before, as depicted in the series.
- As an Octavia she would have been considered a member of the Octavii Rufi, and not a 'woman of the Julii' as she identifies in the series. However, as the great-niece of Caesar she would have politically been considered a Caesarian, and would have owed much of her status to her position in Caesar's extended family.
- There is no historical evidence to suggest that Octavia had sexual relationships with Servilia, Pompey, her brother Octavian or Agrippa, as is dramatized in the series. The real Octavia was celebrated as the model Roman matron in the early Empire, and was buried in the Mausoleum of Augustus.
- Octavia did marry Mark Antony, but was pregnant with her third child by her first husband at the time. When Antony left Rome, he actually settled in Athens, Greece, and not Egypt; Octavia went with him, and she and Antony later had two daughters, Antonia Major and Antonia Minor. Historically, Antony had met Cleopatra and fathered their twins, Alexander Helios and Cleopatra Selene, before marrying Octavia. He did eventually leave Octavia in Greece and reunite with Cleopatra in Egypt; he and Cleopatra later had a third child, Ptolemy Philadelphus (who does not appear in the series). As with the twins, Octavia took custody of Ptolemy and raised him alongside her own children and Antony's children by Fulvia (his first wife who also does not appear in the series).