Philip Prospero, Prince of Asturias was the first son of Philip IV of Spain and Mariana of Austria to survive infancy. Philip IV had no male heir since the death of Balthasar Charles, his son by his first wife, Elisabeth of France, eleven years before, and as Spain's strength continued to ebb the issue of succession had become a matter of fervent and anxious prayer.

Philip IV, also called the Planet King, was King of Spain from 1621 to his death and King of Portugal from 1621 to 1640. Philip is remembered for his patronage of the arts, including such artists as Diego Velázquez, and his rule over Spain during the Thirty Years' War.