The Duke of Viseu is a noble title in Portugal, historically associated with the region of Viseu. The title was first granted in the 15th century and has been held by various members of the Portuguese royal family. It signifies a high rank in the nobility and is often linked to significant land ownership and influence in the region. The title is also connected to notable figures, such as Prince Henry the Navigator, who played a crucial role in the Age of Discoveries. The Duke of Viseu has been an important part of Portuguese history, representing the country's aristocratic heritage and its exploration endeavors.