Macedonian king of Egypt (reigned 107–88 BC) who, under the direction of his mother, Cleopatra III, ruled Egypt alternately with his brother Ptolemy IX Soter II and around 105 became involved in a civil war in the Seleucid kingdom in Syria.

Son of Ptolemy VIII Euergetes II, Ptolemy Alexander was sent to Cyprus as governor in 114 after the opposition of the people of Alexandria prevented his mother from securing the kingship of Egypt for him. When, at the instigation of the queen mother, his elder brother, Ptolemy Soter, was expelled from Egypt in 110, Ptolemy Alexander was recalled from Cyprus and replaced him as coregent in Egypt. Following a reconciliation in early 109, Soter returned and occupied the throne, while Ptolemy Alexander departed for Cyprus as king of the island. Another bitter quarrel between his brother and mother brought Ptolemy Alexander back to Egypt as coregent in 107, but Cleopatra III took official precedence and was the actual ruler.

While the queen mother continued to pursue the family dispute, Ptolemy Alexander found himself drawn into a civil war in the Seleucid kingdom, after his brother lent active aid to the opponents of his mother's allies. With the queen's death in 101 the war ended, and Ptolemy Alexander was reconciled with his brother and even married Soter's daughter, Berenice III.

In 89 the army in Alexandria turned against Ptolemy Alexander, and he was forced into exile. After gathering a mercenary force in Syria-Palestine, the king returned the following year, but when he plundered the temple-tomb of Alexander the Great in Alexandria to pay his troops, the infuriated populace of the city expelled him again, and he was killed at sea between Lycia in Asia Minor and Cyprus. His widow, who had accompanied him into exile, subsequently returned to Egypt to become his brother Soter's queen.

Ptolemy Alexander extended the rights of Egyptian natives, who pressed for further extensions. In 88, the year of his death, a rebellion erupted in the region of Thebes in Upper Egypt with the aim of establishing a native dynasty; this was finally suppressed under his predecessor and successor, Ptolemy IX.