43 BCCenturies: 2nd century BC - 1st century BC - 1st century
- April 14 - Battle of Forum Gallorum: Mark Antony, besieging Caesar's assassin Decimus Brutus in Mutina, defeats the forces of the consul Pansa, but is then immediately defeated by the army of the other consul, Hirtius.
- April 21 - Cicero's 14th and last Philippic.
- April 21 - Antony is again defeated in the Battle of Mutina by a coalition of Octavian, Decimus Brutus, and the two consuls of the year. Antony withdraws into Transalpine Gaul (France).
- July-August – Antony is again at the head of a large army, and Octavian enters Rome in force without opposition. It is clear that Cicero’s plan to divide them against each other has failed.
- November - Octavian meets Antony and Lepidus in Bononia, and the three enter into an official five-year autocratic pact, the Second Triumvirate.
- Lugdunum (Lyon) is founded