An interregnum (plural interregna or interregnums) is a period of discontinuity or "gap" in a government, organization, or social order. Archetypally, it was the period of time between the reign of one monarch and the next (coming from Latin inter-, "between" and rēgnum, "reign" [from rex, rēgis, "king"]), and the concepts of interregnum and regency therefore overlap. Historically, the longer and heavier interregna were typically accompanied by widespread unrest, civil and succession wars between warlords, and power vacuums filled by foreign invasions or the emergence of a new power. A failed state is usually in interregnum.
The term also refers to the periods between the election of a new parliament and the establishment of a new government from that parliament in parliamentary democracies, usually ones that employ some form of proportional representation that allows small parties to elect significant numbers, requiring time for negotiations to form a government. In the UK, Canada and other "first past the post" electoral systems, this period is usually very brief, except in the rare occurrence of a hung parliament as occurred both in the UK in 2017 and in Australia in 2010. In parliamentary interregnums, the previous government usually stands as a caretaker government until the new government is established.
First Interregnum in Scotland, which lasted from either 19 March 1286 or 26 September 1290 until 17 November 1292. The exact dating of the interregnum depends on whether the uncrowned Margaret, Maid of Norway was officially queen before her death in 1290. It lasted until John Balliol was crowned King of Scots.
The Ottoman Interregnum, from 8 March 1403 until 1413, a result of the death of Sultan Bayezid I at the hands of Central Asian warlord Timur (Tamerlane). A period of civil war ensued as none of Bayezid's sons could establish primacy. The crisis was resolved when one of his sons, Mehmed, defeated and killed his brothers and reestablished the Empire.
From 1481 until 1483 in the Kingdom of Norway, during a conflict over the succession of John, during the period of the Kalmar Union. The Norwegian Council of the Realm initially refused to accept the hereditary succession of John; as they asserted that Norway was an elective monarchy. When no serious opposition candidate emerged, the Council relented and elected John. There was also an interregnum from 1533 to 1537, after the dead of Frederick I and the interregnum ended with a coup d'état by his son Christian III.
A brief interregnum occurred in Thailand between 13 October and 1 December 2016 upon the death of King Bhumibol Adulyadej. The crown prince Vajiralongkorn, in an unprecedented move, did not assume the throne immediately after the death of the previous monarch. He asked for time to mourn while he continued functioning in his role as the crown prince. During this period, Prem Tinsulananda served as the regent pro tempore.
In some monarchies, such as the United Kingdom, an interregnum is usually avoided due to a rule described as "The King is dead. Long live the King", i.e. the heir to the throne becomes a new monarch immediately on his predecessor's death or abdication. This famous phrase signifies the continuity of sovereignty, attached to a personal form of power named Auctoritas. This is not so in other monarchies where the new monarch's reign begins only with coronation or some other formal or traditional event. In the Polish–Lithuanian Commonwealth for instance, kings were elected, which often led to relatively long interregna. During that time it was the Polish primate who served as an interrex (ruler between kings). In Belgium the heir only becomes king upon swearing before the parliament.
The Old Kingdom Trilogy takes place after 200 years of interregnum, where the reigning Queen and her two daughters were murdered by Kerrigor, 180 years of regency first and 20 years of anarchy following the death of the last Regent.
The Vlad Taltos series is set in a fantastical world of magic, at a time directly following a 250-year interregnum wherein traditional sorcery was impossible due to the orb being destroyed.
In the world of the Elder Scrolls, there was an Interregnum in the Second Era when the Second Cyrodillic Empire collapsed. It led to just over four centuries of bickering between small kingdoms and petty states. The Interregnum ended when Tiber Septim, or Talos, formed the Third Empire after a decade of war. Similarly, with the sacrifice of Martin Septim during the Oblivion Crisis in the Third Era, the Septim dynasty came to an end, and a seven-year interregnum occurred before Titus Mede I restored the throne and ushered in the Fourth Era.
In Poland by James A. Michener, 1983, an historical novel that spent 38 weeks on The New York Times Best Seller List, interregnum is mentioned numerous times in the ever-shifting power struggles that plagued that country, even up to the 1980s.