Aulus Hirtius (c. 90 – 43 BC) was one of the consuls of the Roman Republic and a writer on military subjects.

He was a legate of Julius Caesar's starting around 58 BC and served as an envoy to Pompey in 50. It was reported that Hirtius dined with Caesar, Sallust, Oppius, Balbus and Sulpicus Rufus on the night after Caesar's famous crossing over the Rubicon river into Italy on 10 January 49 BC.

During the Roman Civil Wars he served in Spain; he may have been a tribune in 48, and in 47 was at Antioch. He was a praetor in 46 and governor of Transalpine Gaul in 45.

After Caesar's assassination in March 44, Hirtius was deeply involved in the maneuvering between parties. Having been nominated for that post by Caesar, Hirtius and Pansa became consuls in 43.

Initially a supporter of Mark Antony, Hirtius was successfully lobbied by Cicero, who was a personal friend, and switched his allegiance to the senatorial party. He then set out with an army to attack Antony who was besieging Mutina. In concert with Pansa and Octavian (the future Emperor Augustus), Hirtius compelled Antony to retire but was slain in the fighting (around 25 April or 27 April). He was honored with a public funeral, along with Pansa who died a few days later.

Hirtius added an eighth book to Caesar's De Bello Gallico and is the likely author of De Bello Alexandrino. The ancients thought he also wrote the De Bello Africo and De Bello Hispaniensi, but it is now considered more likely that he acted as an editor. Hirtius' correspondence with Cicero was published in nine books, but has not survived.

Suetonius in Chapter 68 of his Life of Augustus writes that Lucius Antonius, the brother of Mark Antony, accused Augustus for having "given himself to Aulus Hirtius in Spain for three hundred thousand sesterces." This alleged homosexual liaison must have taken place in 46 BC during the civil wars when Julius Caesar took Octavian to Spain and Aulus Hirtius was serving there. At the time the future Emperor Augustus was 17 years old.

Source: Wikipedia, the free encyclopedia