Tractatus de Purgatorio Sancti Patricii

Tractatus de Purgatorio Sancti Patricii (Treatise on Saint Patrick's Purgatory) is a Latin text written about 1180–1184 by a monk who identified himself as H. of Saltrey.

The author is traditionally known as Henry, though this was an insertion and invention of Matthew of Paris and has been contested in the influential work of historian Jacques le Goff.

Henry states that his source was Gilbert, a monk in Lincoln who visited Ireland in 1148 to found a monastery at Baltinglass in County Wicklow.

The narrative of Owein's visit begins with an account of how the knight was moved to make reparation for his sins after attending confession.

Their prior gave Owein advice on how he should complete his journey safely, by calling on the name of Jesus Christ if ever he found himself in difficulty.

Shortly after the men had departed Owein heard a great roar and a vast number of demons rushed towards him.

He interviewed two Irish abbots about the purgatory and bishop Florentianus, who gives an account of a hermit living near Lough Derg who is visited by demons.

The Tractatus was arguably the most popular vision of Purgatory throughout the Middle Ages and survives in over 30 versions in almost every European vernacular.

Among the most famous versions of the Tractatus is the Anglo-Norman translation the Legend of the Purgatory of St. Patrick by Marie de France.