Biblioteca de Castilla y León, Regional library in Plaza de la Trinidad, Valladolid, Spain.

The Biblioteca de Castilla y León occupies the Palacio de los Condes de Benavente on Plaza de la Trinidad in Valladolid. Created by Law 9/1989 of 30 November, it serves as the head of the Castile and León library system. Its collection includes books, newspapers, maps, scores, recordings and photographs, with most items on open access and available for loan.

The facility opened in 1989 and developed into the central library for the autonomous community of Castile and León. Since then it has served as an important knowledge center for the region and its people.

The library keeps author collections donated by private libraries of literary and cultural figures, notably those given by the Fundación Jorge Guillén. It also manages the Biblioteca Digital de Castilla y León, which offers free online access to digitised works by Castilian and Leonese authors and on regional themes, with more than 33,000 works in 2023.

The library occupies the Palacio de los Condes de Benavente on Plaza de la Trinidad, in the historic centre of Valladolid. Most of the collection is on open shelves and can be borrowed, while the reserve holdings are for consultation and research. The building is wheelchair accessible. The Biblioteca Pública del Estado de Valladolid operates as a section within it.

The library keeps the legal deposit for Castile and León since powers were transferred by Royal Decree 3019/1983, so a copy of every work published in the region reaches the palace. Its Jorge Guillén Foundation author collections came as donations of private libraries. In 2023 it recorded 383,334 visits and 744,808 items.