Demetrius Zvonimir (, ; died 1089) was a King of Croatia and Dalmatia from 1075 or 1076 until his death in 1089. Zvonimir also served as Ban of Croatia (1064–1074), and was named Duke of Croatia in around 1075. His native name was Zvonimir, but adopted the forename Demetrius at his coronation.
He first served as ban in the service of King Peter Krešimir IV. Afterwards, Peter Krešimir IV appointed him duke and declared him as his heir. In 1075 or 1076, Demetrius Zvonimir succeeded to the Croatian throne through papal diplomacy. His reign is characterized as relatively peaceful, with no extensive war campaigns, focused instead on Croatia's economic and cultural development. He inherited the Croatian state at its height and ruled from the city of Knin. Medieval legends allege his assassination, but his death and succession are subjects of controversy in historiography. His reign was followed by a period of anarchy, which ended with the ascension of the Hungarian Árpád dynasty and the creation of a union with Hungary.
Early years
Zvonimir's exact origin and background are uncertain. It is believed that he was a member of the native Trpimirović dynasty, and some historians have proposed that he is a descendant of Svetoslav Suronja's son Stjepan Svetoslavić which also allowed for the thesis that he began his career as Ban of Slavonia. Others rejected his Trpimirović descent and argued he was a member of some other prominent Croatian noble family possibly from Sidraga županija, but his early marriage to Árpád's princes shows he must have been of some extraordinary lineage. In the historical sources are also mentioned his magistro ("teacher") Scestaki (Šestak), and uncle Strezata (Streza) to whom allowed gathering tax in Mosor and from Solin to Bijaći.
Banates of Slavonia and Croatia
During the reign of King Peter Krešimir IV, his relative also through the Orseoli family of Venice, it is conjectured that Zvonimir initially administered Slavonia, specifically the land between the rivers Drava and Sava, with the title of ban. The term "Slavonia" () at the time referred to both modern day Slavonia and North-West Croatia, but there's lack of evidence for such a thesis.
The neighboring Holy Roman Empire under Henry IV invaded Hungary in 1063 to restore Solomon, husband of his sister, to the Hungarian throne. Hungary was then ruled by Solomon's uncle Béla I, whose third daughter Helen was engaged to Zvonimir. According to Chronicon Pictum, Croatia was also attacked around 1063 by the Carantanian army of Ulric I, who occupied a part of Kvarner and the eastern coast of Istria, the "March of Dalmatia". Since the Croatian king was preoccupied with rebellion in Dalmatia, also due to the prohibition of Slavic liturgy, Zvonimir was compelled to seek protection from then King Solomon instead. Géza I and Solomon helped Zvonimir in restoring authority between 1064 and 1067 in the "March of Dalmatia". After they jointly repelled the Carantanians from Croatia, Zvonimir sent many gold, silver and other valuables to Solomon and Géza I as a sign of gratitude. Shortly afterwards in 1070 Zvonimir is first mentioned as a Ban of Croatia in three charters from Zadar, succeeding Ban Gojčo. Croatian charters at the time were issued in the names of both King Peter Krešimir and Ban Zvonimir.
In March 1074, Normans from southern Italy, led by Count Amico of Giovinazzo, invaded Dalmatia on the invitation of Dalmatian cities and Byzantium. They stayed and ruled over the cities of Split, Trogir, Biograd na Moru and Zadar, but also managed capturing a certain Croatian king whose name is not mentioned, but certainly meant King Peter Krešimir, who died by November 1074. Norman crisis lasted until February 1075, when Venice expelled Amico and his forces from Dalmatia. Zvonimir probably helped Venice in the process. Although the Venetians freed Dalmatia and Croatia, with the doge Domenico Selvo even self-titling himself as the doge of Venice, Dalmatia and Croatia (later only of Dalmatia), the Venetians with their mischievous behavior and close contacts with the Byzantium and Holy Roman Empire were not favourable to the Holy See. In such events the Holy See and Zvonimir came into contact with mutual interest.
Meanwhile, another contender for the throne, Stephen II Trpimirović, who had also been the Duke of Croatia until 1066 under King Petar Krešimir, relinquished his claim and relocated later to the Church of St. Stephen beneath the pines in the vicinity of Split, where he was to live a secluded life. It seems that Zvonimir was chosen as an heir to the throne already during Petar Krešimir's late life.