The Union of Utrecht was a treaty signed in 1579 by several northern provinces of the Spanish Netherlands. It marked a significant step in the struggle for independence from Spanish rule during the Eighty Years' War. The agreement united the provinces in their fight against oppression and established a framework for mutual defense and cooperation. This union is often considered a foundational moment for the later formation of the Dutch Republic. It emphasized principles of religious tolerance and self-governance, setting the stage for the eventual independence of the Netherlands from Spain in 1648.