Ptolemy IX Soter II[note 1] (Greek: Πτολεμαῖος Σωτήρ, Ptolemaĩos Sōtḗr 'Ptolemy the Saviour'), commonly nicknamed Lathyros (Λάθυρος, Láthuros 'chickpea'),[3] was twice King of Ptolemaic Egypt.

He eventually quarrelled with his mother and in 107 BC, she deposed him and replaced him with his younger brother, Ptolemy X.

He reigned alone until 81 BC, when he appointed his daughter Berenice III as co-regent shortly before his own death.

Around 117 BC, Ptolemy IX was sent to Cyprus, reportedly at his mother's request, where he served as governor of the island (strategos, nauarchos, archiereus, archikynegos).

[11] However, Chris Bennett argues that it is a false story that was invented by Cleopatra III at a later date.

He points out that Justin's story assumes that Cleopatra III was the only living queen at the time of Ptolemy VIII's death.

[16][11] Meanwhile, Ptolemy IX married his younger sister, Cleopatra Selene, with whom he soon had a daughter, Berenice III.

Instead, in documents from this period, the royal couple were Cleopatra III and Ptolemy IX, who were integrated into the Ptolemaic dynastic cult as the Theoi Philometores Soteres (The Mother-loving Saviour Gods).

Pausanias claims that Cleopatra III wounded a number of her own eunuch servants and displayed them to the people as evidence that her son had attempted to have her assassinated, causing the Alexandrians to riot and expel Ptolemy IX from the city.

Apion protected his position by publishing a will which left all his territories to Rome in the event that he died without heirs, a method which was often used by Hellenistic kings to prevent rivals from attempting to depose or assassinate them.

[22][18] In 103 BC, the new Hasmonean King Alexander Jannaeus led an army to conquer Ptolemais Akko.

The city appealed to Ptolemy IX for help and he sailed over and caused Jannaeus to lift his siege.

He then invaded Galilee, defeated Jannaeus in a battle at Asophon near the River Jordan, and despoiled Judaea with impunity.

Ptolemy X invaded Phoenicia by sea and then marched inland to Damascus, while Cleopatra III besieged Ptolemais Akko.

Ptolemy IX spent the winter encamped at Gaza, before deciding to sail back to Cyprus in early 102 BC.

[18] The army and people of Alexandria turned against Ptolemy X in spring 88 BC and expelled him from Egypt.

[24] When Ptolemy IX returned to Egypt, the south of the country had been under the control of Egyptian rebels since 91 BC.

Ptolemy sent a large force south in November 88 BC, under the command of the general Hierax.

A Roman embassy led by the senator Lucius Memmius, arrived in Egypt in 112 BC.

Papyrus letters survive that instruct all local officials to treat him with the greatest respect and provide him with the most luxurious accommodation.

[31] The historian John Whitehorne noted that the existence of those two children is doubted and they might have died at a young age.

[34] However, John Pentland Mahaffy and Christopher Bennett argue that they were considered illegitimate simply because their mother had not been a co-regnant queen.

[35] Bennett noted that Berenice III's legitimacy was never questioned by ancient historians, and the illegitimacy of Ptolemy IX and Cleopatra IV's marriage makes it more probable that Berenice III was the result of a legitimate marriage, that is between her father and Cleopatra Selene.