Royal fifth

The royal fifth (quinto real or quinto del rey in Spanish and Portuguese) is an old royal tax that reserves to the monarch 20% of all precious metals and other commodities (including slaves) acquired by his subjects as war loot, found as treasure or extracted by mining. The 'royal fifth' was instituted in Medieval Muslim states, Christian Iberian kingdoms and their overseas colonial empires during the age of exploration.

The 'royal fifth' has a dual origin. In Christian kingdoms, it partly comes from the Medieval legal conception of seigneural or regalian rights over the natural patrimony, which assigned to the monarch or feudal overlord original property rights over all unclaimed, undiscovered and undeveloped natural resources (e.g. precious metals in the subsoil, salt in the rock, virgin forests, fish in the sea, etc.) within his jurisdiction. Consequently, private individuals who extracted these natural resources owed compensation to their original 'owner' (the monarch).