The Aisne is a river in northeastern France. It is a left tributary of the Oise. It gave its name to the French department of Aisne. It was known in the Roman period as Axona.
The river rises in the forest of Argonne, at Rembercourt-Sommaisne, near Sainte-Menehould. It flows north and then west before joining the Oise near Compiègne. The Aisne is 356 kilometres long. Its main tributaries are the Vesle, the Aire and the Suippe. The Battle of the Axona was fought near there between the Romans and the Belgae in 57 BC. Three Battles of the Aisne were fought in the Aisne valley during the First World War.