William IX, Marquis of Montferrat

William IX Palaeologus (10 August 1486 – 4 October 1518) was Marquis of Montferrat from 1494 until his death. He was a member of the House of Palaeologus-Montferrat, a cadet branch of the Palaiologos dynasty which had once ruled the Byzantine Empire.

William IX
Macrino d’Alba, Ritratto di Guglielmo IX Paleologo; Tempera su tavola; Crea, Santuario dell’Assunta e Tesoro del Santuario.jpg
Portrait by Macrino d'Alba
Marquis of Montferrat
PredecessorBoniface III Palaiologos
SuccessorBoniface IV Palaiologos
Born10 August 1486
Died(1518-10-04)4 October 1518
Noble familyPalaeologus-Montferrat
Spouse(s)Anna d'Alençon
FatherBoniface III, Marquis of Montferrat
MotherMaria of Serbia
Coat-of-arms on a coin (testone) of William IX.


He was the son of Marquis Boniface III and Maria of Serbia. At the time when he succeeded his father (1494), William was still a minor. At first, his mother acted as regent. After her death (1495), regency passed to his mother's cousin Constantine Komnen-Arianiti (1495-1499).[1]

He continued the pro-French policy of his father and, in 1508, he married to princess Anna d'Alençon, daughter of René d'Alençon. During the Italian Wars, in 1513, he protected the French retreat from Milan; however, to avoid retaliation from Maximilian Sforza William was forced to pay him 30,000 scudi.

The Milanese Duke did not respect the treaty, and his troops invaded Montferrat and sacked numerous cities. At the same time, informed that his relative Oddone, Marquis of Incisa, was trying to obtain the title of Marquis of Montferrat, William marched to Incisa and occupied that lordship. Oddone and his son Badone were sentenced to death. However, the annexation was later declared null by Holy Roman Empire diplomacy, but in the subsequent year, William was able to maintain the new lands.

He had 3 children with Anna d'Alençon:

He died in 1518 and was succeeded by his son Boniface IV, initially with his mother Anne d'Alençon as regent.[2]


  1. ^ Haberstumpf 2009, p. 191.
  2. ^ Haberstumpf 2009, p. 199.


  • Haberstumpf, Walter (2009). Regesti dei Marchesi di Monferrato (secoli IX-XVI). Alessandria: San Giorgio Editrice. ISBN 9788876790935.
William IX, Marquis of Montferrat
Born: 10 August 1486 Died: 1518
Preceded by
Boniface III
Marquis of Montferrat
Succeeded by
Boniface IV