The Cailly (French pronunciation: [kaji]) is a river in Normandy, France, 29 kilometres (18 mi) in length, flowing through the department of Seine-Maritime. It is a right tributary of the Seine.

The Cailly has its source in the territory of the commune of Cailly. Taking a southward journey, it flows through Fontaine-le-Bourg, meeting its principal tributary, the Clérette at Montville. It then flows through Malaunay, Houlme, Notre-Dame-de-Bondeville, Maromme, Déville-lès-Rouen and finally Rouen where it joins the Seine on its right bank.

The average flow of the Cailly at Notre-Dame-de-Bondeville is 2.6 m / second.

In the 18th and 19th centuries, the valley was filled with textile mills, which earned it the nickname la petite Manchester, (Little Manchester).

• Albert Hennetier, Aux sources normandes: Promenade au fil des rivières en Seine-Maritime, Ed. Bertout, Luneray, 2006 ISBN 2867436230

• French water management scheme