The Act of Abjuration is the declaration of independence by many of the provinces of the Netherlands from the allegiance to Philip II of Spain, during the Dutch Revolt. Signed on 26 July 1581 in The Hague, the Act formally confirmed a decision made by the States General of the Netherlands in Antwerp four days earlier. It declared that all magistrates in the provinces making up the Union of Utrecht were freed from their oaths of allegiance to their lord, Philip, who was also King of Spain. The grounds given were that Philip had failed in his obligations to his subjects, by oppressing them and violating their ancient rights (an early form of social contract). Philip was therefore considered to have forfeited his thrones as ruler of each of the provinces which signed the Act.

The Act of Abjuration allowed the newly independent territories to govern themselves, although they first offered their thrones to alternative candidates. When this failed in 1587 by, among other things, the Deduction of François Vranck the provinces became a republic in 1588. During that period the largest parts of Flanders and Brabant and a small part of Gelre were recaptured by Spain. The partial recapture of these areas to Spain led to the creation of Staats-Vlaanderen, Staats-Brabant, Staats-Overmaas and Spaans Gelre.