Sosibius

thumb|Gold Ancient drachma|octadrachm of [[Ptolemy IV Philopator (British Museum).]] Sosibius (; floruit 221-204 BC) was the chief minister of Ptolemy IV Philopator (221–204 BC), king of Egypt. Nothing is known of his origin or parentage, though he may have been a son of Sosibius of Tarentum; nor is there any account of how he rose to power. He is first attested immediately after the accession of Ptolemy IV in 221 BC, exercising great influence over the 22-year old king alongside Agathocles, the brother of Ptolemy IV's mistress Agathoclea. He remained a major force throughout the reign and helped ensure the smooth succession of Ptolemy V Epiphanes in 204 BC. After that he disappears from the record. ==Life== ===Accession of Ptolemy IV=== The historian Polybius characterises him as "the pseudo-guardian of Ptolemy [who] seemed to be a shrewd and long-lasting tool, but was ever doing evil in the kingdom." and says he was responsible for a purge of the royal family which took place shortly after Ptolemy's accession. Ptolemy IV's uncle Lysimachus was probably murdered at this time. His mother Berenice II was believed to support his younger brother Magas, who had held substantial military commands and was popular with the army, so Magas was scalded to death in his bath. Berenice II died shortly afterwards; she is said to have been poisoned. ===Fourth Syrian War===

The Seleucid king Antiochus the Great invaded Coele-Syria in 221 BC. He was rebuffed by the Ptolemaic governor of the region, Theodotus, and forced to turn east as a result of the revolt of his satrap of Media, Molon, but in spring 219 BC he attacked once more, beginning the Fourth Syrian War and quickly captured most of Coele-Syria. Polybius says that this occurred because Ptolemy had given himself up to luxury, leaving all administration of the kingdom to Sosibius, who neglected the finances and military defences.