The Treaty of Alcáçovas was a pivotal moment in the history of Iberian relations, formally concluding hostilities between the Kingdom of Castile, represented by the Catholic Monarchs, Ferdinand II of Aragon and Isabella I of Castile, and the Kingdom of Portugal, under King Afonso V. Years of rivalry and conflict had strained the two kingdoms over territorial disputes and colonial ambitions, prompting negotiations to restore peace. The treaty was signed on September 4, 1479, significantly in the town of Alcáçovas, near the city of Évora, Portugal.

Under the terms of the treaty, a clear demarcation was established between Castilian and Portuguese territorial claims, particularly in the Atlantic Ocean. Castile was granted control over the Canary Islands, which had been a focal point of contention, while Portugal retained rights over its islands, such as the Azores and Madeira. This division not only defined their colonial possessions but also established a basis for future expeditions undertaken by both nations during the Age of Discovery.

The treaty included provisions that facilitated trade and diplomatic relations between the two kingdoms, marking a critical step toward a more cooperative approach in European politics. Afonso V’s recognition of Isabella and Ferdinand's claims helped legitimize their rule and emboldened Spain’s aspirations across the Atlantic. The event also played a crucial role in shaping the dynamics of colonial competition as both kingdoms looked to expand their influence in the Americas, a quest that would lead to profound global ramifications in the following centuries.