Avignonet massacre: A group of Cathars, with the probable connivance of Count Raymond VII of Toulouse, murdered the inquisitor William Arnaud and eleven of his companions.

The Avignonet massacre occurred on the eve of 28 May 1242 when a small force, mainly consisting of Cathars, massacred a group of inquisitors during the Albigensian Crusade.

Catharism was a Christian quasi-dualist and pseudo-Gnostic movement which thrived in northern Italy and southern France between the 12th and 14th centuries. Denounced as a heretical sect by the Catholic Church, its followers were attacked first by the Albigensian Crusade and later by the Medieval Inquisition, which eradicated the sect by 1350. Around one million were slaughtered, hanged, or burnt at the stake.

Raymond VII was Count of Toulouse, Duke of Narbonne and Marquis of Provence from 1222 until his death.

William Arnaud or Guillaume Arnaud was a Dominican inquisitor and martyr.

May 28 is the 148th day of the year in the Gregorian calendar; 217 days remain until the end of the year.