San Millán de Yuso is a historic monastery located in the La Rioja region of Spain. It was founded in the 6th century and is known for its beautiful Romanesque architecture. The monastery is part of the San Millán de la Cogolla complex, which also includes the nearby San Millán de Suso monastery. The site is significant for its role in the development of the Spanish language, as it houses some of the earliest written texts in the language. In 1997, San Millán de Yuso was designated a UNESCO World Heritage Site, recognizing its cultural and historical importance.