The Treaty of Corbeil was an agreement signed on 11 May 1258, in Corbeil (today Corbeil-Essonnes, in the region of Île-de-France) between Louis IX of France and James I of Aragon.
The French king, as the heir of Charlemagne, renounced feudal overlordship over the counties of the Marca Hispanica.
James I renounced claims to Fenouillet-du-Razès and Peyrepertuse, with the castle of Puilaurens, the castle of Fenouillet, the Castellfisel, the castle of Peyrepertuse and the castle of Quéribus; moreover he renounced his feudal overlordship over Toulouse, Saint Gilles, Quercy, Narbonne, Albi, Carcassonne (part of the County of Toulouse since 1213), Razès, Béziers, Lauragais, Termes and Ménerbes (enfeoffed in 1179 to Roger III of Béziers); to Agde and Nîmes (their viscount was recognized as the feudatory of the Counts of Barcelona from 1112), and Rouergue, Millau and Gévaudan (derived from the inheritance of Douce of Provence). Under his lordship remained the viscounty of Carlat and the lordship of Montpeller with the barony of Aumelas.
The renunciation of the feudal rights of the King of Aragon over the County of Foix, initially included in the treaty, was rejected by the king of Aragon on ratifying the document on 16 July 1258, on the grounds that it was not under the overlordship of the king of France.
According to this treaty the daughter of James I, Elisabeth, would marry Philip, heir of Louis IX.
On 17 July, the Aragonese king renounced his hereditary rights to the County of Provence (then an imperial fief) in favor of Marguerite, daughter of Ramon Berenguer IV, Count of Provence, his uncle (died in 1245) and wife of the French king.
The direct result of the treaty was to definitively separate the House of Barcelona-Aragon from the politics of today's southern France. A secondary effect is that it allowed the transfer of Provence to the Capetian House of Anjou, and after extinction of that house, its incorporation into France.