Châtelaillon-Plage (French pronunciation: [ʃatɛlajɔ̃ plaʒ], also [ʃɑtɛlajɔ̃]), commonly known as Châtelaillon, is a commune in the Charente-Maritime department, administrative region of Nouvelle-Aquitaine, France.

In the 16th century near the point of Cornard today featured a fortress known as Castrum Allionis, the old capital of Aunis.

The rest of the fortress were totally despaired in the 16th century, a small hamlet with bells of the swamps.

At the end of the nineteenth century, it was linked with rail, it constructed its first baths bains de mar with numerous villas.

Châtelaillon is twinned with Knebworth, Hertfordshire, England,[3] Evolène, Wallis, Switzerland, and Skierniewice, Łódź, Poland.