A feud letter (German: Fehdebrief or Absagebrief) was a document in which a feud was announced, usually with few words, in medieval Europe. The letter had to be issued three days in advance to be legally valid.

To prevent the feud from becoming a case of murder and thus become punishable by law, those involved had to abide by the following rules:

"Wettet, biscop Dierich van Moeres, dat wy den vesten Junker Johan van Cleve lever hebbet alls Juwe, unde wert Juwe hiermit affgesaget"
("Know this, Bishop Dietrich of Moers, that we prefer the steadfast Junker, John of Cleves, to you, and hereby give you notice thereof.")