The siege of Harfleur Normandy France began 18 August 1415 and ended on 22 September when Harfleur surrendered to the English.

On Tuesday 13 August 1415 Henry V of England landed at Chef-en-Caux in the Seine estuary. Then he attacked Harfleur with 2000 men of arms and 6000 bowmen. The garrison of 100 men was reinforced by two experienced knights, the Sieur d-Estouteville and the Sieur de Gaucourt, who arrived with a further 300 men-at-arms and took command.

On the 18 August, the Duke of Clarence led part of the army to set-up camp on the far, east side of the town. This meant that the town was invested and a French relief convoy, bearing supplies of guns, powder, arrows and crossbows was captured. Details of the siege are not well known but seem to have followed the standard pattern of late medieval siege warfare and after the walls had been seriously damaged by the twelve great guns in the English siege train, Henry planned a general assault one month to the day that the town had been enveloped. But the town's commanders asked for a parley and terms were agreed that if the French army did not arrive before the 22nd then the town would surrender to the English. Harfleur yielded to the invaders on September 22. The knights were released on parole to gather ransom, and the town's people who were prepared to swear allegiance to Henry were allowed to remain, while the rest were ordered to depart.

During the siege the English army had be hard hit by dysentery which continued to affect them after the siege ended. Henry left a small garrison in the town and on Monday 8 October set out with the rest of his army to go to Calais. He searched for an undefended or weakly defended bridge or ford on the Somme river hoping to slip past the French army but although he crossed the Somme he fail to evade the French army and was forced to fight the Battle of Agincourt.