Siege of Trebizond (1205–06) in the context of "Seljuk Sultanate of Rûm"

Alexios I Megas Komnenos (Greek: Αλέξιος Κομνηνός; Georgian: ალექსი კომნენოსი; c. 1182 – 1 February 1222) or Alexius I Megas Comnenus with his brother David, the founder of the Empire of Trebizond and its ruler from 1204 until his death in 1222. The two brothers were the only male descendants of the Byzantine Emperor Andronikos I, who had been dethroned and killed in 1185, and thus claimed to represent the legitimate government of the Empire following the conquest of Constantinople by the Fourth Crusade in 1204. Although his rivals governing the Nicaean Empire succeeded in becoming the de facto successors, and rendered his dynastic claims to the imperial throne moot, Alexios' descendants continued to emphasize both their heritage and connection to the Komnenian dynasty by later referring to themselves as Megas Komnenos ("grand Komnenos").

While his brother David conquered a number of Byzantine provinces in northwestern Anatolia, Alexios defended his capital Trebizond from an unsuccessful siege by the Seljuk Turks around the year 1205. Further details of his reign are sparse. Muslim chroniclers record how, in 1214, Alexios was captured by the Turks in the field while defending Sinope; despite sending an envoy to seek their surrender the city refused to capitulate to Sultan Kaykaus I, and Alexios was tortured in sight of the Sinopians. The city submitted to Kaykaus and Alexios was freed after becoming Kaykaus' vassal. Alexios died at the age of forty.