Ptolemy X Alexander I (Greek: Πτολεμαῖος Ἀλέξανδρος, Ptolemaĩos Aléxandros) was the Ptolemaic king of Cyprus from 114 BC until 107 BC and of Egypt from 107 BC until his death in 88 BC. He ruled in co-regency with his mother Cleopatra III as Ptolemy Philometor Soter until 101 BC, and then with his niece and wife Berenice III as Ptolemy Philadelphus. He was a son of Ptolemy VIII and Cleopatra III, and younger brother of Ptolemy IX. His birth name was probably Alexander.
Ptolemy X was the second son of Ptolemy VIII and Cleopatra III. When Ptolemy VIII died in 116 BC, Ptolemy IX became king with Cleopatra III as his co-regent and Alexander was sent to Cyprus to serve as governor. However, in 114–113 BC, he declared himself king. Cleopatra III quarrelled with Ptolemy IX and arranged for Alexander to return to Egypt in 107 BC and replace his brother as co-regent (with modern sources calling him Ptolemy X).
