Ladislaus Posthumus (22 February 1440 - 23 November 1457), king of Hungary as Ladislaus V.; king of Bohemia as Ladislaus I; duke of Austria, the only son of Albert, king of Hungary, 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 Ulászló I, but the infant Ladislaus's mother caused the holy crown to be stolen from its guardians at Visegrad, and 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.
On the death of Ulászló 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 was sent to Vienna to induce the emperor to surrender the child and the holy crown; but only in 1452 did Frederick feel compelled to relinquish both. The child was then transferred to the pernicious guardianship of his mother's cousin, Ulrich Cillei, who corrupted him, soul and body, and inspired him with a jealous hatred of the Hunyadi family.
On 28 October 1453 Ladislaus Posthumus, aged 13, was crowned king of Bohemia, and henceforth spent most of his time at Prague and Vienna. He remained supinely indifferent to the Turkish threat; at the instigation of Cillei did his best to hinder the defensive preparations of John Hunyadi, and fled from the country on the tidings of the siege of Belgrade. On the death of Hunyadi he made Cillei governor of Hungary at the diet of Futtak (October 1456), and when that traitor paid with his life for his murderous attempt on Laszlo Hunyadi at Belgrade (9 November 1456), Ladislaus procured the decapitation of young Hunyadi (16 March 1457), after a mock trial which raised such a storm in Hungary that the king fled to Prague, where he died suddenly (23 November 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.
Original text from 1911 Encyclopedia, please update.
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. Postumus László, Slovak: Ladislav (V) Pohrobok