House of Trastámara (1479–1555)
Under Isabella and Ferdinand, the royal dynasties of Aragon and Castile were united into a single line. Historiography of Spain generally treats this as the formation of the Kingdom of Spain, but in actuality, the two kingdoms continued for many centuries with their own separate institutions. It wasn't until the Nueva Planta decrees of the early 18th century that the two lands were formally merged into a single state.
| Name | Lifespan | Reign start | Reign end | Notes | Family | Image |
|---|---|---|---|---|---|---|
| Ferdinand V of Castile, (II of Aragon)
the Catholic |
10 March 1452 – 23 January 1516 (aged 63) |
15 January 1475 Castile 20 January 1479 Aragon |
26 November 1504 Castile 23 January 1516 Aragon |
Son of John II of Aragon and Juana Enríquez | Trastámara |  |
| Isabella I
the Catholic Spanish spelling: Isabel I |
22 April 1451 – 26 November 1504 (aged 53) |
11 December 1474 Castile |
26 November 1504 Castile |
Daughter of John II of Castile and Isabella of Portugal | Trastámara |  |
| Joanna of Castile
the Mad Spanish spelling: Juana I |
6 November 1479 – 12 April 1555 (aged 75) |
26 November 1504 Castile 23 January 1516 Aragon |
12 April 1555 | Daughter of Isabella I of Castile and Ferdinand II of Aragon | Trastámara |  |
| Philip I
the Handsome Spanish spelling: Felipe I |
22 July 1478 – 25 September 1506 (aged 28) |
27 June 1506 Castile |
25 September 1506 Castile |
Husband of Joanna of Castile | Habsburg |  |
