Leoncio Alonso González de Gregorio y Álvarez de Toledo, 22nd Duke of Medina Sidonia, GE is a Spanish aristocrat and historian. Born in Madrid, Medina Sidonia is the eldest son of Leoncio González de Gregorio y Martí and his wife Luisa Isabel Álvarez de Toledo, 21st Duchess of Medina Sidonia. The Duke is Professor of History at the University of Castile-La Mancha and of the Diplomatic School of the Ministry of Foreign Affairs and Cooperation.