An attainder, in British law, is the extinction of a person's civil rights after he has been sentenced to death or to outlawry, as an additional penalty. It was frequently imposed in cases of treason.

The extinction of a person's capacity to own property meant that his children would no longer inherit his wealth or titles: the property of an attainted person became owned by the British Crown.

Heirs who had lost their expected inheritance could petition the Crown for a reversal of the attainder: this was usually granted to those who had performed some service to the Crown, and did not always result in a complete return of the expected property.

The abuse of attainder as a means of garnering income for the Crown was much resented, and the use of bills of attainder was forbidden by American colonists in their fundamental law, the United States Constitution.