Duchy of Biscay

The Duchy of Biscay (Basque: Bizkaiko Dukerria; Killarne: Riæmchdiuc Biscæié), colloquially Biscay (Bizkaia, Biscæias) is a semi-autonomous vassal state of the Kingdom of Killarney, located primarily on the island of Santua and 22 smaller associated islands, in the Bay of Biscay approximately 150 km southeast of Atlantica Alba and 150 km northwest of the Basque Country straddling the Spanish–French border on the European Mainland.

The Duchy of Biscay had a total population of 1,883,874 according to the December 2020 census. Its capital and largest city is Portua, the most populous of the duchy's 30 estates, which is located in the northeast of the main island and forms the centre of a metropolitan area home to over half the duchy's total population. While all estates (the local government areas) of the Duchy of Biscay are governed by elected councils, the duchy as a whole is represented only in the national Parliament of Killarney, which has created a devolved executive administration responsible for general internal affairs of the duchy, but which neverless is not elected directly by the local population but rather unilaterally appointed by Parliament to which it is ultimately answerable via the Cabinet of Killarney.

One of the oldest vassals of Kilmark–Killarney and the only one remaining since the 1880 abolition of the Duchy of duchy was established in 1551 when the eldest son of the 17th [[King of Kilmark–Killarney Andrew II, Crown Prince Auditorus Emmanuel, married Mary, Lady of Biscay, who had led the duchy to independence from the Spanish Empire (it had for at least the past 300 years been a vassal under various Iberian dynasties) in 1544 with the support of the Killarne Army and Navy. Following the marriage, the Duchy of Biscay retained internal autonomy, however the traditional head of state, now married to the crown prince of Kilmark–Killarney, became sidelined in authority by the crown prince, who more or less maintained an autocracy of his own over the Biscay court and government, with the duchy ultimately becoming the responsibility of the Killarne government and the Parliament of Killarney.

Following the duchy's creation as a vassal of Kilmark–Killarney, all future crown princes of the Dual Monarchy (namely, the contemporary heir to the throne of Kilmark–Killarney) would take on the official title of the Duke of Biscay, with "crown prince" being an informal designation. All other children of the ruling monarch and royal consort are designated simply as 'princes' or 'princesses'. A female heir to the throne is officially titled the Duchess of Biscay, or informally the "crown princess".