Numerius Fabius Ambustus was an ancient Roman commander who was the son of Marcus Fabius Ambustus, and brother to Caeso and Quintus. In 406 BC, he and his forces captured the Volscian city of Anxur (modern Terracina) by securing the high ground above the town, from which they were able to launch attacks against its walls. When the town's defenders attempted to respond to these harassing attacks, the remainder of Numerius' forces used escalade to scale the walls and enter the town. After the victory, his forces began to torture the inhabitants of the city in retaliation for the Volscian massacre of the Roman garrison at Verruga in which the Roman prisoners had been horribly tortured. Numerius eventually showed mercy, and around 2500 Volscians were permitted to surrender with their lives.
Numerius was consular tribune in 406 BC, and again in 390. It was in his second consulship that he and his two brothers were sent as ambassador to the Gauls who were besieging Clusium. During this mission he participated in an attack against the besieging Gauls. The Gauls demanded that the three should be surrendered to them for violating the law of nations. When the Roman Senate refused to give up the guilty parties, the Gauls marched against Rome, which they sacked after the battle of the Allia.
Many scholars believe the entire story of the events at Clusium to be fiction, as Clusium had no real reason to appeal to Rome for help, and the Gauls needed no real provocation to sack Rome. The story, it is hypothesized, exists to provide an explanation for an otherwise unmotivated attack on Rome, and to depict Rome as a bulwark of Italy against the Gauls.
His son was Marcus Fabius Ambustus (consul 360 BC).
This article incorporates text from a publication now in the public domain: Smith, William, ed. (1870). "Ambustus (4)". Dictionary of Greek and Roman Biography and Mythology. 1. p. 141.