Duchy of Castro

{{Short description|Fiefdom in central Italy from 1537 to 1649}}

{{One source|date=June 2022}}

{{expand Italian|Ducato di Castro|topic=hist|date=March 2011}}

{{Infobox country

|native_name = {{native name|it|Ducato di Castro}}
{{native name|la|Ducatus Castri}}

|conventional_long_name = Duchy of Castro

|common_name = Castro

|image_flag = Flag of the Duchy of Parma.svg

|image_coat = Coat of Arms of the Duke Octavius Farnese (1547-1586).svg

|image_map = Ducato di Castro (1640).jpg

|image_map_caption = The Duchy of Castro. Detail from a map by W.J. Blaeu (1640)

|image_map2 = Mappa Lazio Farnese 1640.png

|image_map2_caption = Duchy of Castro and other Farnese possessions in 1640

|era = Early modern era

|government_type = Non-sovereign monarchy

|status = vassal

|empire = the Papal States

|life_span = 1537–1649

|year_start = 1537

|event_start = Created by Pope Paul III

|event1 =

|date_event1 =

|event2 =

|date_event2 =

|year_end = 1649

|event_end = Ranuccio II is forced to cede the lands back to Pope Innocent X

|p1 = Papal States

|flag_p1 = Flag of the Papal States (pre 1808).svg

|p2 =

|flag_p2 =

|s1 = Papal States

|flag_s1 = Flag of the Papal States (pre 1808).svg

|s2 =

|flag_s2 =

|capital = Castro

|latd= |latm= |latNS= |longd= |longm= |longEW=

|national_motto = {{langnf|la|Castrum civitas fidelis|The castle is a faithful city|break=yes}}

|national_anthem =

|common_languages = {{ubl|Latin|Italian}}

|religion = Catholicism

|currency =

|title_leader = Duke

|leader1 = Pier Luigi Farnese (first)

|year_leader1 = 1537–1545

|leader2 = Ranuccio II Farnese (last)

|year_leader2 = 1646–1649

|footnotes =

|today = Italy

}}

The Duchy of Castro was a fiefdom in central Italy formed in 1537 from a small strip of land on what is now Lazio's border with Tuscany, centred on Castro, a fortified city on a tufa cliff overlooking the Fiora River which was its capital and ducal residence. While technically a vassal state of the Papal States, it enjoyed de facto independence under the rule of the House of Farnese until 1649, when it was subsumed back into the Papal States and administered by the House of Stampa di Ferentino.Lunario Romano, Palazzi Municipali del Lazio 1984

It was created a duchy by Pope Paul III (1534–1549) in the bull Videlicet immeriti on 31 October 1537, with his son Pier Luigi Farnese and his firstborn male heirs as its dukes. It lasted approximately 112 years and was eclipsed by the Farnese's possessions in Parma. It stretched from the Tyrrhenian Sea to the Lago di Bolsena, in the strip of land bounded by the river Marta and the river Fiora, stretching back to the Olpeta stream and the lago di Mezzano, from which the Olpeta flows. The duchy of Latera and county of Ronciglione were annexed to it.

The title of Duke of Castro has been held since the late 1860s by the claimant to the headship of the House of Bourbon-Two Sicilies, since the Kingdom of the Two Sicilies was annexed to the newborn Kingdom of Italy. Prince Carlo, Duke of Castro currently holds the tile.