Château-Thierry (French: [ʃa.to.tje.ri]) is a French commune situated in the department of the Aisne, in the administrative region of Picardy and in the historic Province of Champagne.

The origin of the name of the town is unknown. The local tradition attributes it to Thierry IV, the penultimate Merovingian king, who was imprisoned by Charles Martel, without a reliable source. Château-Thierry is the birthplace of Jean de La Fontaine and was the location of the First Battle of the Marne and Second Battle of the Marne. The region of Château-Thierry (the arrondissement, to be exact) is called the country of Omois. Château-Thierry is one of 64 French towns to have received the Legion of Honour.