king of Egypt (reigned 44–30 BC), son of Julius Caesar and Cleopatra VII. Ptolemy was his mother's co-ruler, killed by Octavian, later the emperor Augustus, after Cleopatra's death in 30.

Ptolemy was the child of Cleopatra and Caesar, although a few classical authors, perhaps for political reasons, expressed doubts about his paternity. After Cleopatra's arrival in Rome in 46, Caesar himself, however, officially recognized the child as his son. When his father was assassinated in 44, Cleopatra returned with the boy to Egypt, where she probably arranged the death of her younger brother, Ptolemy XIV Theos Philopator II, to make room for her son on the throne. Her ambition was to make Caesarion Caesar's successor, although in the meantime she remained first in the royal succession.

After Cleopatra had begun her liaison with Mark Antony, the Roman triumvir of the East, Caesarion appeared at Alexandria in 34 with the title “King of Kings,” while his mother called herself “Queen of Kings.” Following Antony's disastrous defeat at Actium in 31 during the war against his fellow triumvir Octavian, Cleopatra sent Caesarion to Berenice, a seaport on the Red Sea coast of Upper Egypt; but Octavian lured him back to Alexandria, where the young king was executed.