56 BC

By place

Roman Republic

• Consuls: Gnaeus Cornelius Lentulus Marcellinus and Lucius Marcius Philippus.
• Clodia accuses her former lover Marcus Caelius Rufus of trying to poison her. The trial ends with the defendant acquitted thanks to the Pro Caelio speech of Marcus Tullius Cicero. There is no further mention of the previously famous Clodia.
• Third year of Julius Caesar's Gallic Wars:
• * Decimus Junius Brutus Albinus defeats the Veneti of Brittany: The Gauls lose most of their warships to the Romans in a sea battle at modern-day Quiberon Bay. The strongholds on the coast are stormed, and the population is slaughtered or sold into slavery.
• * Autumn - Julius Caesar leads an attack on the Morini and the Menapii tribes of the Belgae on the North Sea. They withdraw into their forests, creating difficulties for Caesar's supply lines. The onset of bad weather forces him to pull back into Gallia Belgica.

  Britain

• This year, or possibly the following year, the king of the Trinovantes called Imanuentius, is overthrown and killed by his rival Cassivellaunus. His son Mandubracius flees to Gaul and appeals to Julius Caesar for help.