Louis IX (25 April 1214 – 25 August 1270), commonly Saint Louis, is King of France from 1226 until his death.

He is also styled Louis II, Count of Artois from 1226 to 1237.

Born at Poissy, near Paris, he is a member of the House of Capet, the son of Louis VIII and Blanche of Castile.

He works with the Parliament of Paris in order to improve the professionalism of his administration in regards to legal actions.

He is the only canonized king of France; consequently, there are many places named after him, most notably São Luís do Maranhão, Brazil, St. Louis, Missouri, in the United States and both the state and city of San Luis Potosí, in Mexico.

On 11 June 1256, the General Chapter of the Trinitarian Order formally affiliates Louis IX at the famous monastery of Cerfroid, which had been constructed by Felix of Valois north of Paris.