Alexius II Comnenus (1167-1183), Byzantine emperor (1180-1183), was the son of emperor Manuel I Comnenus and Maria, daughter of Raymund, prince of Antioch, and was born at Constantinople on September 10, 1167.

On Manuel's death in 1180, Maria, who had been immured in a convent under the name of Xene, had herself proclaimed regent (1179-1180), and handing over her son to counsellors, who encouraged him in every vice, supported the government of Alexius the protosebastos (a cousin of Alexius II), who was popularly believed to be Maria's lover. The young Alexius and his friends now tried to form a party against the empress mother and the protosebastos; and his sister Maria, wife of Caesar John, stirred up riots in the streets of the capital.

Their party was defeated (May 2, 1182), but Andronicus Comnenus took advantage of these disorders to aim at the crown, entered Constantinople, where he was received with almost divine honours, and overthrew the regents. His arrival was celebrated by a massacre of the Latins in Constantinople, especially the Venetian merchants, which he made no attempt to stop. He allowed Alexius to be crowned, but forced him to consent to the death of all his friends, including his mother, his sister and the Caesar, and refused to allow him the smallest voice in public affairs.

The betrothal in 1180 of Alexius with Agnes, daughter of Louis VII of France, a child of nine, was quashed, and he was married to Irene, daughter of Andronicus. Andronicus was now formally proclaimed as co-emperor, and not long afterwards, on the pretext that divided rule was injurious to the Empire, he caused Alexius to be strangled with a bow-string (October 1183).