Corrected entry: Pompeius and Caesar were not the only two Consuls as depicted in the series. There was a third one named Crassus as well.
Son of Hades - S2-E2
Corrected entry: Vorenus declares that he is the Son of Hades. Hades was a Greek god, the Romans called him Pluto or Dis. He should have called himself a son of Pluto, not Hades.
Correction: Vorenus would have been well aware of the Greek god Hades and that could have been a character choice. It's not a secret that Hades and Pluto are the same Deity, and with Rome having a Greek quarter during this period, Vorenus would have been exposed to both names.
Corrected entry: During the dinner scene where Octavian confronts his family and Marc Anthony about their various infidelities, he refers to Agrippa as "a low born Pleb". This is done to amplify the disgrace to Marc Anthony of his wife having an affair with Agrippa. But the real Agrippa definitely was not a Pleb but a member of the Equestrians, the second tier of Roman aristocracy. This can be easily confused as in 43AD Agrippa became Tribute of the Plebs. But this office was open to both Plebs and Equestrians by this time, but not Patricians such as Octavian. Given Octavian's thoroughness, it is hard to believe this is a character mistake.
Correction: Even though one may agree that calling Marcus Vipsanus Agrippa a lowly pleb is harsh, Gaius Julius Caesar Octavianus was in his right to do it. Yes, Agrippa was an equestrian of the second tier of the Roman nobility, but this tier were also plebeians or plebs. Only patricians like Octavian are not considered plebs in ancient Rome, and EVERYONE else (not slaves or freedmen though), no matter how rich or powerful, were in the legal sense plebs. Even Pompeius Magnus and Cicero.
Corrected entry: It is made out in Series 2 as if Livia is Octavian's first wife. In fact she was his third wife. In reality his marriages to his two previous wives only lasted 2 years in total so historically they were much less relevant than Livia, the mother of Tiberius, the next Emperor.
Correction: Creative license. The show also leaves out Brutus' wife, several of Antony's wives and Octavia's husbands, along with a number of children. They have to leave some people out, or the show would have too many characters to focus on. Furthermore, while it is IMPLIED that Livia is his first wife, it's never actually STATED. He could have been married before when he was living with Agrippa.
Corrected entry: At the time the series is set the height of the average Roman foot soldier is estimated by historians to be about 5 feet 4 inches. A big chap like Pullo would have looked like he was surrounded by Hobbits in battle. The Celtic peoples that the Romans fought tended to be significantly taller due to a better diet than Mediterranean people. The small battle shown in the first episode is therefore not strictly accurate. As more Central and Northern Europeans were recruited by the Romans the average height of the army rose. Excess character height tends to be a mistake in all historical dramas and would be extremely difficult for the directors to correct.
Correction: When real people are portrayed in films, the actor or actress is often the wrong height, as acting ability generally takes precedence over exact appearance. Likewise many other physical factors (age, hair colour, weight) take second place to the quality of the performance when casting. In a nutshell, using actors of the wrong physical appearance is completely standard in films. As such, in common with other standard movie conventions, this sort of thing is not considered to be a mistake.
Corrected entry: Quintus Pompey introduces himself as Quintus Valerius Pompey. If he is the son of Gnaeus Pompey, then his name would be simply Quintus Pompey, not Quintus Valerius Pompey. Adding the name 'Valerius' makes him a member of the gens Valeria, i.e. an entirely different family.
Correction: Quintus is the natural son of Pompey, as stated several times on the show. The name Quintus Valerius Pompey shows that he is Pompey's son, but born into the Valerius family.
Corrected entry: Brutus expresses to Caesar how sorry he is to hear that Caesar's daughter Julia has died. Brutus was actually engaged to Julia, before Caesar married her to Pompey for political reasons.
Correction: It is far from certain it was Brutus who was engaged to Julia. We know that Julia was engaged to one Quintus Servilius Caepio and that Brutus was for some time known as Quintus Servilius Caepio Brutus, having been adopted by his uncle Quintus Servilius Caepio. Some writers have stated that Caepio and Brutus are the same, but others have rejected this theory.
How Titus Pullo Brought Down the Republic - S1-E2
Corrected entry: There was no Roman named Marc Anthony, the man who was a friend of Caesars and later husband of Cleopatra was named Marcus Antonius. If they called him Marc Anthony at all times in the series that wouldn't be a mistake, since it would be "modernized" language, but in this episode they at one point refer to him as Marcus Antonius. If they acknowledge that this is his name it is an error for them to call him Marc Anthony in other scenes because it makes no sense.
Correction: The only time they call him Marcus Antonius, is when he is installed as a tribune of the plebs. That is an official ceremony, where he is likely to be called by his full name. Mark Anthony is the name everyone calls him by in daily business. I have a friend called Marcus, whom I always just call Marc.
Corrected entry: When Julia dies at childbirth she is lying down on a bed. Roman women gave birth sitting in a chair.
Correction: She's not giving birth anymore, she's dying and saying farewell to Pompey. So they probably moved her from the chair to a bed.
Corrected entry: Pullo falls asleep while he's on guard. Soldiers who fell asleep on their guard were sentenced to death. Yet Vorenus, who is a very by-the-books man, only gets annoyed. A centurion would have executed the soldier in question.
Correction: That's a character choice, and not necessarily a plot hole. In this case, Vorenus would have no opportunity to have placed Pullo under arrest or have him tried before returning to camp, and much can have happened to make him overlook this fault in the meantime. They have won a battle together (against overwhelming odds), they have accomplished their "impossible" mission, and return as heroes with Caesar's newly-rescued grand-nephew.
Corrected entry: When Atia is having sex with the owner of the white stallion she is on top. In ancient Rome that would never happen, as whoever was on top during sex was the dominant one, and no man would consider a woman dominant over him.
Correction: A women of her stature and class would certainly be dominant over that particular man. Or if that would never be the case, maybe he just liked it that way, many people who are dominate in real life will choose to be submissive in bed. Also just because it was generally accepted that people on top where dominate, it does not mean that ever single person in the whole history of the Roman Empire believed it to be true, and followed the practice.
Corrected entry: Atia of the Julii was in real life a religious and caring woman, considered by historian Tacitus to be the ideal Roman matron. She was definitely not a cheap trollop as depicted in the series.
Correction: The filmmakers do not claim to be historically accurate.
Correction: The series are accurate. There were only two consuls in ancient Rome, not three. Apart from that, Marcus Licinius Crassus died in 53 BC and the series start somewhere after that.