Aisne (ancient Axona), river, northern France, a tributary of the Oise River. It rises in the Forest of Argonne, flows north-west for the first two-fifths of its course, and then flows west to the Oise, which it joins above Compiègne. The Aisne is about 280 km (175 mi) long; more than 160 km (100 mi) are navigable, and canals connect it with the Meuse and Marne rivers. The river was the scene of major battles during World War I.