Constable of Castile () was a title of a military nature created by John I, King of Castile in 1382, as a result of the Third Fernandine War against the Portuguese and the English.
The post substituted the title of Alférez Mayor del Reino and was more consistent with that of the French Constable of France. The constable was the second person in power in the kingdom, after the King and had supreme authority over the Army, as well as broad jurisdictional powers.
In 1473, Henry IV of Castile made the title hereditary for the Velasco family and the dukes of Frías. By that time, the position lacked any substance, and therefore it was decided that the title would lose all military or administrative functions, becoming a purely honorific distinction.
List of constables of Castile 1382–1391: Alfonso of Aragon and Foix 1393–1400: Pedro Enrique de Trastámara, son of Fadrique Alfonso of Castile 1400–1423: Ruy López Dávalos 1423–1453: Álvaro de Luna 1458–1473: Miguel Lucas de Iranzo
Hereditary ceremonial title 1473–1492: Pedro Fernández de Velasco, 2nd Count of Haro 1492–1512: Bernardino Fernández de Velasco, 1st Duke of Frías 1512–1528: Íñigo Fernández de Velasco, 2nd Duke of Frías 1528–1559: Pedro Fernández de Velasco, 3rd Duke of Frías 1559–1585: Íñigo Fernández de Velasco, 4th Duke of Frías 1585–1615: Juan Fernández de Velasco, 5th Duke of Frías 1615–1652: Bernardino Fernández de Velasco, 6th Duke of Frías 1652–1696: Íñigo Melchor de Velasco, 7th Duke of Frías 1696–1713: José Fernández de Velasco y Tovar, 8th Duke of Frías
Sources Portal de Archivos Españoles