Nicholaus Kanabus was elected Emperor of the Byzantine Empire during the 4th Crusade on 25 or 27 January 1204 by an assembly of the Byzantine Senate, priests, and the mob of Constantinople in direct opposition to co-emperors Isaac II and Alexios IV. Nicholaus was a young noble (probably a relative of Angelid emperors) who was chosen after three days of sorting through several unwilling candidates and refused to assume the lofty position. Though popularly chosen, he never accepted imperial power, and took Sanctuary in the bowels of Hagia Sophia. Alexios V "Mourtzouphlos", who had deposed Emperors Isaac II and Alexios IV, offered him a prominent position in his own administration, but Nicholaus adamantly rejected these terms. On February 8, after rebuffing an imperial summons, Emperor Nicholaus Kanabus was dragged out of the church, in which he had sought refuge, and strangled on the ornate marble steps of Hagia Sophia.
The contemporary historian Niketas Choniates described Nicolaus Kanabus as a kind, gentle and intelligent man.