Alexios Komnenos, latinised as Alexius Comnenus, and sometimes called Alexios the Younger, was the eldest son of the Byzantine emperor John II Komnenos and his wife Eirene of Hungary. He was crowned co-emperor in 1119, at 13 of age, but predeceased his father in 1142. He was an elder brother of the emperor Manuel I Komnenos, and had a twin sister, Maria Komnene.

Prōtostratōr was a Byzantine court office, originating as the imperial stable master. Its proximity to the imperial person led to a highly visible role in imperial ceremonies, and served as a springboard for several capable individuals, like Manuel the Armenian or the future emperors Michael II and Basil I the Macedonian, to reach the highest offices. From the mid-11th century, the post rose in importance, becoming more an honorific dignity for senior members of the court, than an actual office. From the 13th century on, the post could be held by several persons, and ranked eighth in the overall hierarchy of the court. Throughout its history, it was a title often borne by senior military commanders. The female form of the title, given to the wives of the prōtostratores, was prōtostratorissa (πρωτοστρατόρισσα).