Nassau-Dillenburg was a historical principality in the region of Hesse, Germany. It was part of the larger House of Nassau, which played a significant role in European history. The principality was established in the late 16th century and was known for its influence during the Reformation and the Thirty Years' War. The territory of Nassau-Dillenburg included the town of Dillenburg, which served as its capital. The ruling family, the Nassau family, produced several notable figures, including William of Orange, who was a key leader in the struggle for Dutch independence. The principality eventually merged into larger states, contributing to the formation of modern Germany.