Ladislaus Posthumus (22 February 1440 - 23 November 1457), king of Hungary as Ladislaus V (or VI); king of Bohemia as Ladislaus I; duke of Austria, the only son of Albert II, Holy Roman Emperor, and of Elizabeth, daughter of the emperor Sigismund, was born at Komarom four months after his father's death, and was hence called Ladislaus Posthumus (Ladislaus the Posthumous).

The estates of Hungary had already elected Ladislaus III of Poland as their king Vladislaus I (Hungarian: I. Ulászló), but the infant Ladislaus's mother caused the holy crown to be stolen from its guardians at Visegrad and have it brought to Wiener Neustadt by a lady of the court, Helene Kottannerin . According to legend, the cross on the crown is askew, because it was damaged during the transport. Ladislaus' mother thus compelled the primate to crown the infant king at Székesfehérvár on 15 May 1440; whereupon, for safety's sake, she placed the child in the guardianship of his uncle, the emperor Frederick III (then ruler of Styria and Carinthia), who held him prisoner in Castle Orth and ruled Austria himself.

On the death of Wladislaus I in the Battle of Varna (10 November 1444), the Hungarian estates, not without considerable opposition, elected Ladislaus Postumus as their king and sent a deputation to Vienna to induce the emperor to surrender the child and the holy crown, which Frederick first refused. In Bohemia George of Poděbrady, acted as regent, and in Hungary John Hunyadi. From 1450 onwards, the pressure of the Austrian estates to free Ladislaus grew. In 1452, they entered into the Mailberg Confederation under the leadership of Ulrich of Eyczing and Ulrich Cillei and freed him by force. Cellei, the cousin of Ladislaus' mother, prevailed against Eyczing and became the guardian of the child, and thus the effective ruler in his stead.

On 28 October 1453 Ladislaus Posthumus, aged 13, was crowned king of Bohemia, and henceforth spent most of his time at Prague and Vienna. As Cillei became increasingly inimical towards John Hunyadi, who bore the main burden of the battle against the Ottomans, Cillei (and with him Ladislaus) remained supremely indifferent to the Turkish threat. After the death of Hunyadi, Ladislaus made Cillei governor of Hungary at the diet of Futtak (October 1456). When, after the siege of Belgrade, Cillei was murdered by Laszlo Hunyadi in revange for his assassination attempt on him on November 9, 1456, Ladislaus procured the decapitation of young Hunyadi, who was executed on March 16, 1457. This raised such a storm in Hungary that Ladislaus had to flee to Prague, where he spent the last year of his life.

He died suddenly on November 23, 1457), while making preparations for his marriage with Magdalena, daughter of Charles VII of France. He is rumored to have been poisoned by his political opponents in Bohemia, though no actual evidence of this exists. In Austria, his uncle Frederick V succeeded him, in Hungary Matthias Corvinus of the Hunyadi family, while in Bohemia George of Poděbrady was to become the only Hussite ruler of his kingdom.

Note: There is one major error in the 1911 Encyclopedia entry for Ladislaus. The entry states that Ladislaus' mother's father (i.e. his maternal grandfather) was Emperor Sigismund, and then states that he was placed under the guardianship of his maternal grandfather, Ulrich Cillei. Ulrich was in fact his mother's first cousin.

Names in other languages: Czech: Ladislav (I) Pohrobek, Hungarian: V.(or VI) Postumus László, Slovak: Ladislav (V or VI) Pohrobok