The Asiento de Negros (lit. 'agreement of blacks') was a monopoly contract between the Spanish Crown and various merchants for the right to provide enslaved Africans to colonies in the Spanish Americas. The Spanish Empire rarely engaged in the transatlantic slave trade directly from Africa itself, choosing instead to contract out the importation to foreign merchants from nations more prominent in that part of the world, typically Portuguese and Genoese, but later the Dutch, French, and British. The Asiento did not concern French or British Caribbean, or Brazil, but only Spanish America.
The 1479 Treaty of Alcáçovas divided the Atlantic Ocean and other parts of the globe into two zones of influence, Spanish and Portuguese. The Spanish acquired the west side, washing South America and the West Indies, whilst the Portuguese obtained the east side, washing the west coast of Africa – and also the Indian Ocean beyond. The Spanish relied on enslaved African labourers to support their American colonial project, but now lacked any trading or territorial foothold in West Africa, the principal source of slave labour. The Spanish relied on Portuguese slave traders to fill their requirements. The contract was usually obtained by foreign merchant banks that cooperated with local or foreign traders, that specialized in shipping. Different organisations and individuals would bid for the right to hold the asiento.
