The siege of Avignon (500) saw the Burgundian king Gundobar hold off a besieging Frankish army led by Clovis I for long enough to convince Clovis to offer peace terms.
Clovis had invaded Burgundy at the invitation of Gundobar's brother Godegesil. Their combined army inflicted a heavy defeat on Gundobar at the battle of the Ouche, but Gundobar escaped from the battlefield and fled to Avignon. At this point Godegesil made a serious error of judgement. Instead of accompanying Clovis to the siege of Avignon he decided to occupy the Burgundian capital at Vienne, presumably believing that his brother was doomed.
Gregory of Tours' account of the siege suggests that Gundobar shared his brother's view of his chances until Aridius, one of his advisors came up with a plan that offered some hope. Aridius suggested that Gundobar needed to hold out in Avignon until Clovis's mood had softened. Aridius would pretend to change sides, and go to Clovis's camp in an attempt to win him over.
The plan worked just as Aridius has planned. He was welcomed at Clovis's court outside Avignon, and spent some time making himself popular. Clovis appears not to have had any siege equipment, and instead prepared to blockade the city. With no sign that Gundobar was ready to surrender this would have been a lengthy process, and Aridius picked this as his moment. He pointed out how strong the defences of Avignon were, and how little impact Clovis would have even if his army ravaged the surrounding areas. He suggested instead that Clovis should offer peace terms, leaving Gundobar alive and on his throne in return for an annual tribute. The absent Godegesil was unable to argue his case, and Clovis agreed to follow Aridius's suggestion.
Gundobar accepted Clovis's terms, and paid the first tribute. Clovis withdrew back into his own kingdom, leaving Gundobar and Godegesil as the joint kings of Burgundy. After a short gap Gundobar turned on his brother, leading an army to besiege Vienne (c.500-501). When food began to run short Godegesil expelled the civilian population of the city, a second mistake. Amongst the refugees was the man in charge of the aqueduct, who showed Gundobar how to get into the city through the aqueduct. Godegesil was killed in the fighting, leaving Gundobar as the sole ruler of Burgundy.