The Battle of Philippi is the final battle in the Wars of the Second Triumvirate between the forces of Mark Antony and Octavian (of the Second Triumvirate) and the forces of Julius Caesar's assassins Marcus Junius Brutus and Gaius Cassius Longinus in 42 BCE, at Philippi in Macedonia.

The Second Triumvirate declares this civil war to avenge Julius Caesar's murder.The battle consists of two engagements in the plain west of the ancient city of Philippi.

The first occurs on the first week of October; Brutus faces Octavian, while Antony's forces are up against those of Cassius.

At first, Brutus pushes back Octavian and enters his legions' camp.

But to the south, Cassius is defeated by Antony, and commits suicide after hearing a false report that Brutus had also failed.

Brutus rallies Cassius' remaining troops and both sides order their army to retreat to their camps with their spoils, and the battle is essentially a draw, but for Cassius' suicide.

A second encounter, on 23 October, finishes off Brutus's forces, and he commits suicide in turn, leaving the triumvirate in control of the Roman Republic.