Demetrius of Montferrat

Demetrius or Demetrios of Montferrat (Italian: Demetrio di Monferrato; Greek: Δημήτριος Μομφερρατικός, Dēmētrios Momferratikos), (Thessalonica, 1205 – 1230 in Amalfi), was king of Thessalonica from 1207 to 1224.

Demetrius was the son of Marquis Boniface of Montferrat by Margaret of Hungary, the widow of Emperor Isaac II Angelos. In the aftermath of the Fourth Crusade Boniface had secured for himself the kingdom of Thessalonica in the division of the spoils. Marrying the former Byzantine empress, he found it easier to attract support from the members of the Byzantine aristocracy. When Boniface's son was born in 1205, he was named after Saint Demetrius, the patron saint of Thessalonica.

Boniface was killed in a battle against the Bulgarians in 1207, and Kaloyan of Bulgaria promptly besieged Thessalonica. The siege ended with Kaloyan's murder, but Demetrius' rule was not secure. The most influential magnates of the kingdom conspired against him, plotting to replace the infant ruler with his half-brother, Marquis William VI of Montferrat. The Latin Emperor Henry of Flanders determined to stem this movement and advanced on Thessalonica in December 1208. The barons, led by Count Umberto II of Biandrate, shut the gates of the city before the emperor and issued several unreasonable demands. The emperor pretended to accept Biandrate's terms (provided that Margaret accepted them) long enough to gain entrance into the city. Margaret was instructed to overrule the terms and Henry crowned young Demetrius king on January 6, 1209 and extracted oaths of homage from the Lombard barons. The emperor's actions were confirmed by Pope Innocent III.

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