The Marian reforms of 107 BC were a group of military reforms initiated by Gaius Marius, a statesman and general of the Roman republic. Up until the last decade of the second century BC the eligibility requirements to become a Roman soldier in the service of the Republic were very strict.

When war threatened, the consuls of the day would be charged with the duty of recruiting an army from the eligible citizenry of the Republic. As a rule one of the consuls would lead this mainly volunteer army into battle. As can be imagined, not all elected consuls were adept at leading an army. For example, in the year 113 BC the consul Gnaeus Papirius Carbo was defeated at the Battle of Noreia by invading tribes of the Cimbri and the Teutons, losing all but 20,000 men out of an army of 200,000. This disaster was followed by a protracted war in Africa against King Jugurtha of Numidia.