The Battle of the Tolenus River was fought on 11 June 90 BC[1][note 1] between the Roman Republic, led by the consul Publius Rutilius Lupus, and an army of Marsian Rebels commanded by Titus Vettius Scato.

While Lucius Caesar marched against the Samnites, Rutilius was sent to face the Marsi, selecting Gaius Marius as his senior legate.

[3] Marius, downstream from the attack, observed bodies floating down the river and therefore decided to advance across the river, taking Scato's undermanned camp by surprise and forcing Scato to retreat with his ambush force in search of provisions.

Despite the equal losses, the battle was unquestionably a Roman defeat with the death of the consul Rutilius.

The senate decided against holding elections to replace Rutilius, instead handing control of his army jointly to Marius and Quintus Servilius Caepio.