The Duke of Medina Sidonia is a hereditary title in the Spanish nobility. The current holder of the title is Leoncio Alonso González de Gregorio y Martí, who is the 22nd Duke of Medina Sidonia. The title has a long history and is associated with the town of Medina Sidonia in the province of Cádiz, Spain. The Duke of Medina Sidonia has historically been an important figure in Spanish history and has been associated with the Spanish Armada and other significant events.