Medina de Rioseco is a municipality located in the province of Valladolid, in the autonomous community of Castile and León and Spain.

The coat of arms shield is quartered, with two castles in gold and two horses leaning out of colored battlements on a silver background, surrounded by a wreath of laurel leaves, but no crown.

During the Middle Ages, in the Merindad of Valladolid Infantazgo (in old Castilian cited as: Meryndat del Infantadgo de Ualladolid), there was an administrative division of the Kingdom of Castile, which is described in the book Calif of Behetrías of Castile,[2] drafted by the Cortes of Valladolid of 1351, when the establishment of knights applied to King Pedro I to absorb the Behetrías land by conversion to manors.

Exercising dominion, D. Fadrique Enriquez, second admiral, was granted by John II the privilege of conducting an annual fair.

Medina de Rioseco became the global trading hub for silver arriving from the Indies through the port of Seville and enjoyed an economic boom that reached its peak during the 16th century.

Four large Riosecano churches were built, and the city became home to one of the most important fairs of the kingdom, second only to that at Medina del Campo.