| Stephen IV | |
|---|---|
 Stephen IV depicted in the Illuminated Chronicle | |
| King of Hungary and Croatia contested by Stephen III | |
| Reign | 27 January 1163 – 19 June 1163 |
| Coronation | 27 January 1163, Székesfehérvár |
| Predecessor | Ladislaus II |
| Successor | Stephen III |
| Born | c. 1133 |
| Died | 11 April 1165 (aged 31–32) Zimony (now Zemun in Serbia) |
| Spouse | Maria Komnene |
| House | Árpád dynasty |
| Father | Béla II of Hungary |
| Mother | Helena of Rascia |
| Religion | Roman Catholic |
Stephen IV (Hungarian: IV. István, Croatian: Stjepan IV, Slovak: Štefan IV; c. 1133 – 11 April 1165) was King of Hungary and Croatia, ascending to the throne between 1163 and 1165, when he usurped the crown of his nephew, Stephen III. He was the third son of Béla II of Hungary, and when his conspiracy against his brother Géza II failed, he was exiled from Hungary in the summer of 1157. He first sought refuge in the Holy Roman Empire, but received no support from Emperor Frederick I. Shortly afterwards he moved to the Byzantine Empire, where he married a niece of Emperor Manuel I Komnenos, Maria Komnene, and converted to the Eastern Orthodox Church.
After Géza II died on 31 May 1162, Emperor Manuel attempted to assist Stephen against his nephew and namesake, Stephen III, in seizing the crown. Although the Hungarian lords were willing to leave their young monarch, they sharply opposed Stephen and elected his brother, Ladislaus II, king. Ladislaus II granted the ducatus, or duchy, which included one-third of the kingdom, to Stephen. Ladislaus II died on 14 January 1163, and Stephen succeeded him. Lucas, Archbishop of Esztergom, who remained a staunch supporter of the expelled young Stephen III, denied to crown him and excommunicated him. Stephen IV remained unpopular among the Hungarian lords, enabling his nephew to muster an army. In the decisive battle, which was fought at Székesfehérvár on 19 June 1163, the younger Stephen routed his uncle, forcing him once again to flee Hungary.
Stephen attempted to regain his crown with the assistance of Manuel I and Frederick I, but both emperors abandoned him. Emperor Manuel settled him in Syrmium, a province acquired from Hungary. He died of poisoning by his nephew's partisans during the siege of Zimony (now Zemun in Serbia).