The Temple of Mars Ultor was a sanctuary erected in Ancient Rome by the Roman Emperor Augustus in 2 BCE and dedicated to the god Mars in his guise as avenger. The centerpiece of the Forum of Augustus, it was a peripteral style temple, on the front and sides, but not the rear, raised on a platform and lined with eight columns in the Corinthian order style.
According to Suetonius and Ovid, the young Octavian vowed to build a temple to Mars in 42 BCE just before the Battle of Philippi if the god would grant him and Marcus Antonius victory over two of the assassins of Julius Caesar, Gaius Cassius Longinus and Marcus Junius Brutus. However, work did not commence on the temple until after the recovery of the Aquilae in 20 BCE that had been lost by Marcus Licinius Crassus in the disastrous Battle of Carrhae 33 years earlier. Originally, the Roman Senate had decreed that the returned standards were to be housed in a temple to Mars Ultor that was to be built on the Capitoline Hill. Augustus however, declared that he would build it at his own expense on the site of his new forum.