The English monarch that oversaw the Spanish Armada's defeat was Queen Elizabeth I. Her reign during the late 16th century marked a pivotal moment in English history, especially with the defeat of the Spanish Armada in 1588. This victory symbolized the rise of England as a major naval power and the decline of Spanish dominance. Elizabeth's leadership, strategic alliances, and the mobilization of the English fleet played crucial roles in this successful defense, boosting national pride and solidifying her legacy as one of England’s most revered monarchs.