Ptolemy X (Ptolemy Alexander), d. 80 B.C., king of ancient Egypt (80 B.C.), of the Macedonian dynasty, son of Ptolemy IX. His stepmother, Cleopatra Berenice, was joint ruler with her father, Ptolemy VIII, and sole ruler after his death until the Romans under Sulla brought about her marriage to Ptolemy X, who became joint ruler. A few days later he murdered her, and the Alexandrians rose up and killed him.
