The Siege of Paris of 885–86 is part of a Viking raid on the Seine, in the Kingdom of the West Franks.

The siege is the most important event of the reign of Charles the Fat, and a turning point in the fortunes of the Carolingian dynasty and the history of France.

It also proves to the Franks the strategic importance of Paris, at the time only a small island town.

The siege is the subject of an eyewitness account in the Latin poem Bella Parisiacae urbis of Abbo Cernuus.With hundreds of ships, and possibly tens of thousands of men, the Vikings arrive outside Paris in late November 885, at first demanding tribute.

This is denied by Odo, Count of Paris, despite that he only can assemble a couple hundred soldiers to defend the city.

The Vikings attack with a variety of siege engines, but fail to break through the city walls after some days of intense attacks.

The siege is upheld after the initial attacks, but without any significant offense for months thereafter.

As the siege goes on, most of the Vikings leave Paris to pillage further upriver.

The Vikings make a final unsuccessful attempt to take the city during the summer, and in October, Charles the Fat arrives with his army.To the frustration of the Parisians who had fought for a long time to defend the city, Charles stops short of attacking the Viking besiegers, and instead allows them to sail further up the Seine to raid Burgundy (which is in revolt), as well as promising a payment of 700 livres (pounds; 257 kg).

Odo, highly critical of this, tries his best to defy the promises of Charles, and when Charles dies in 888, Odo is elected the first non-Carolingian king of the Franks.