The House of Trastámara was a royal dynasty that ruled over Spain and parts of Europe from the late 14th century to the early 16th century. It originated from the union of the Kingdom of Castile and the Kingdom of Aragon, significantly influencing the political landscape of the Iberian Peninsula. The dynasty is known for its role in the unification of Spain and the establishment of a powerful monarchy. Key figures of the House of Trastámara include Isabella I of Castile and Ferdinand II of Aragon, whose marriage in 1469 united their kingdoms. This union laid the groundwork for the eventual formation of modern Spain. The dynasty also played a crucial role in the Spanish Inquisition and the exploration of the New World.