The siege of Vellaunodunum (early 52 B.C.) was the first of three Roman attacks on Gallic towns that forced Vercingetorix to abandon his siege of Gorgobina early in the Great Gallic Revolt of 52 B.C.
Having failed to prevent Caesar from reaching his legions in their winter quarters Vercingetorix moved to attack the Boii town of Gorgobina, somewhere in the tribal lands of the Aedui. Caesar had allowed the Boii to settle in Gaul in 58 B.C., and this attack forced him to move his legions out of their winter quarters and move south in an attempt to force Vercingetorix to lift the siege.
Leaving two legions and his baggage at Agendicum (Sens), Caesar advanced south, reaching Vellaunodunum, a town of the Senones tribe after two days (variously identified at Beauns, Montargis or Château-Landon). According to his commentaries he decided to attack the town to avoid leaving an enemy in his rear, although he probably also hoped that a series of attacks on Gallic towns would force Vercingetorix to abandon his own siege of Gorgobina.
The siege of Vellaunodunum only lasted three days. By the end of the second day the Romans had built their line of circumvallation around the town, and on the third day ambassadors from the town asked for surrender terms. Caesar demanded that they surrender all of their arms, provide him with all of their cattle and surrender 600 hostages. The town's leaders agreed to these terms, and leaving Caius Trebonius to conduct the actual surrender Caesar moved on to attack Cenabum.