Reichsacht (engl. Imperial Ban) was a form of outlawry in the Holy Roman Empire. At different times, it could be declared by the Holy Roman Emperor, by courts like the Vemgericht or the Reichskammergericht, or by the Reichstag.

People under Reichsacht, known as Geächtete or Vogelfreie, lost all their rights and possessions. They were legally considered dead and anyone was allowed to rob, injure or kill them without legal consequences. The Reichsacht automatically followed the excommunication of a person, as well as extending to anyone offering help to a person under the imperial ban.

Vogelfreie could reverse the ban by submitting to the legal authority. The Aberacht, a stronger version of the Reichsacht, could not be reversed.

The Reichsacht was sometimes imposed on whole Imperial Estates. In that case, other estates could attack and possibly conquer them. For the banned state that meant that they would loose their Reichsunmittelbarkeit and in the future have a second overlord in addition to the emperor.

Famous people under the imperial ban included:

• 1180 Henry the Lion for refusing military support to Frederick I, Holy Roman Emperor, against Barbarossa

• 1521 Martin Luther and his supporters for spreading heretic beliefs and splitting the church.

• 1546 John Frederick, Elector of Saxony, for sheltering and supporting Luther

Reichsacht