The Authie is a river in northern France whose 108-kilometre (67 mi) course crosses the departement of the Pas-de-Calais and the Somme. Its source is near the village of Coigneux. It flows through the towns of Doullens, Auxi-le-Château, Nempont-Saint-Firmin and Nampont, finally flowing out into the Channel near Berck.

The Pas-de-Calais is a department in northern France named after the French designation of the Strait of Dover, which it borders. It has the most communes of all the departments of France, with 890, and is the 8th most populous. It had a population of 1,465,278 in 2019. The Calais Passage connects to the Port of Calais on the English Channel. The Pas-de-Calais borders the departments of Nord and Somme and is connected to the English county of Kent via the Channel Tunnel.