The monasteries of San Millán de Suso and San Millán de Yuso are two monasteries situated in the village of San Millán de la Cogolla, La Rioja, Spain. They have been designated a World Heritage Site by UNESCO since December 1997.
The two monasteries' names Suso and Yuso mean the "upper" and the "lower" in archaic Castilian, respectively. Suso is the older building and is believed to be built on the site of a hermitage where Saint Emilian lived. Perhaps Suso's major claim to fame is as the place where phrases in the Spanish and Basque languages were written for the first time. UNESCO acknowledges the property "as the birthplace of the modern written and spoken Spanish language". The phrases in Spanish and Basque are glosses on a Latin text and are known as the Glosas Emilianenses. There is some debate as to whether the Spanish words are written in an early form of Castilian or in a related dialect. In either case, San Millán's importance as a cradle of the Spanish language is reinforced by the proximity of the village of Berceo which is associated with Gonzalo de Berceo, the first Spanish poet known by name.