Sibyrtius ( Greek:; lived 4th century BC) was a Greek officer from Crete in the service of Alexander the Great, who was appointed by him, on his return from India (326 BC), governor of the province of Carmania. This post he shortly after exchanged for the more important satrapy of Arachosia and Gedrosia, to which he succeeded on the death of Thoas. At the death of Alexander (323 BC), Sibyrtius, in common with most of the other governors of the remote eastern provinces, retained possession of his satrapy, which was again confirmed to him in the second partition at Triparadisus, 321 BC. In the subsequent divisions which arose among the eastern satraps, Sibyrtius was one of those who supported Peucestas against Peithon and Seleucus, and afterwards accompanied that leader when he joined Eumenes in Susiana, 317 BC. His attachment was, however, to Peucestas, and not to Eumenes, and in the intrigues of the former against his commander-in-chief, Sibyrtius supported him so strongly that he incurred the especial resentment of Eumenes, who threatened to bring him to trial; a fate from which he only escaped by a hasty flight. But this open rupture with Eumenes had the advantage of securing him the favour of Antigonus, who, after the defeat of his rival, confirmed Sibyrtius in his satrapy, and placed under his command a large part of the select body of troops termed Argyraspids; a measure adopted with the ostensible object of guarding these provinces against the neighbouring barbarians, but in reality with a view to the gradual destruction of the troops in question, whose turbulent and disaffected spirit was well known..
Arrian mentions that Megasthenes, the historian and ambassador of Seleucus to India after his 303 BCE treaty with Chandragupta, lived with Sibyrtius, suggesting the latter may have remained at his post as satrap for quite a long time:"Megasthenes lived with Sibyrtius, satrap of Arachosia, and often speaks of his visiting Sandracottus, the king of the Indians."