Casseneuil (French pronunciation: [kasnœj]; Occitan: Cassanuèlh) is a commune in the Lot-et-Garonne department in south-western France.

In July 1214 Robert de Courçon, the papal legate, awarded the territories of Rodez, Albigeois, Quercy and Agenais in perpetuity to Simon IV de Montfort, who promptly set out with an army from Carcassonne to seize his new fief.

Capturing the towns and destroying the castles of the existing lords, he burned the few heretics he found.

However, in late August Casseneuil itself fell and he awarded Dominic de Guzmán and his preachers at Fanjeaux with the rents due from the town, though it is doubtful if they were able to collect them.

His army then moved north to attack Périgord, even though it was not part of his papal grant.