Alexios V Doukas (; – December 1204), in Latinised spelling Alexius V Ducas, was Byzantine emperor from February to April 1204, just prior to the sack of Constantinople by the participants of the Fourth Crusade. His family name was Doukas, but he was also known by the nickname Mourtzouphlos or Murtzuphlus (), referring to either bushy, overhanging eyebrows or a sullen, gloomy character. He achieved power through a palace coup, killing his predecessors in the process. Though he made vigorous attempts to defend Constantinople from the crusader army, his military efforts proved ineffective. His actions won the support of the mass of the populace, but he alienated the elite of the city. Following the fall, sack, and occupation of the city, Alexios V was blinded by another ex-emperor and later executed by the new Latin regime. He was the last Byzantine emperor to rule in Constantinople until the Byzantine recapture of Constantinople in 1261. Origins and character Though in possession of the surname used by a leading Byzantine aristocratic family, there is very little definitely known concerning the ancestry of Alexios Doukas Mourtzouphlos. The noble Doukas clan were not the only Doukai, as the surname was also employed by many families of humble origins. It has been claimed that Alexios Doukas was a great-great-grandson of the emperor Alexios I Komnenos () in the female line (cognatic descent). This is not improbable, as all other Byzantine emperors, and the majority of attempted usurpers, of the period had a connection with the former imperial house of the Komnenoi, either by descent or marriage. A more precise theory has been proposed, that he was the son of an Isaac Doukas, and was the second cousin of Alexios IV Angelos (). A letter sent to Pope Innocent III, stated that Alexios Doukas Mourtzouphlos was 'a blood relation' of Alexios IV Angelos. The contemporary historian Niketas Choniates was dismissed from office as logothete of the sekreta by Mourtzouphlos. His assessment of the emperor's character might therefore be biased; however, Choniates allows that he was extremely clever by nature, though arrogant in his manner and lecherous. Political intrigues and usurpation The participation of Alexios Doukas Mourtzouphlos in the attempted overthrow of Alexios III Angelos () by John Komnenos the Fat in 1200 had led to his imprisonment. Mourtzouphlos was probably imprisoned from 1201 until the restoration to the throne of Isaac II Angelos (), the brother