Ophellas was born in Pella as the son of a Macedonian nobleman named Silenus. He was probably educated at the court of king Philip II (359-336) and queen Olympias, because he was later considered as one of the closest friends of the crown prince, Alexander the Great. We know nothing about Ophellas' youth and career during Alexander's reign (336-323), except for the fact that he was one of the trierarchs during Alexander's return from India. These officials were responsible for the building of the navy, and we know that only the most important courtiers were chosen for this important office (text).
After the death of Alexander, Ophellas sided with Ptolemy, the new satrap of Egypt and another personal friend of Alexander. Ptolemy had understood the situation in Alexander's empire better than anyone else: after the death of the conqueror, it was impossible to keep his possessions together, especially since his brother and successor Philip Arridaeus was mentally unfit to rule. Ptolemy saw that only smaller kingdoms had any chance of survival, and tried to become independent. Arridaeus' regent, Perdiccas, still tried to maintain the empire's unity and attacked Egypt in 320, but after a defeat, he was killed by his own officers Peithon, Antigenes, and Seleucus.
Ptolemy could be successful, because his rear was covered by Ophellas. In 323/322, a Spartan mercenary leader named Thibron had arrived in Cyrenaica, a group of five Greek towns in Libya. He carried with him a large treasure: all Babylonian taxes of the years 330-325. This was sufficient to start a small kingdom, and he had some success. However, the native Libyans appealed to Ptolemy, who recognized an opportunity when he was offered one: he immediately sent Ophellas with a small army to the west, to support the Libyans and occupy Cyrenaica. It was (probably) Ophellas' first independent command, but he was successful: in the winter of 322/321, Thibron was executed, and Cyrenaica and the Libyan tribes allied themselves to Ptolemy. Moreover, the treasure was sent to Egypt. Ptolemy could quietly wait for Perdiccas, knowing that he would not be attacked in his rear. As we have already seen, he won an important victory.
Meanwhile, Ophellas remained in Cyrenaica as Ptolemy's viceroy. He founded a new harbor, called Ptolemais, which was destined to become one of the most important towns in ancient Libya. In 313/312, there was a brief crisis; the details are unclear, but Ophellas stayed on as ruler of Cyrenaica.
In fact, it is possible that he de facto became independent. He was certainly independent in 309, when he allied himself to Agathocles, the tyrant of Syracuse. It is not likely that Ophellas was still collaborating with Ptolemy, because the terms of the treaty between Agathocles and Ophellas were, as we shall see in a moment, not in Ptolemy's advantage.
Agathocles had tried to conquer Sicily. This had brought him into conflict with Carthage, which possessed the western half of this island. In the summer of 311, the Carthaginian general Hamilcar, had won such a complete victory over Agathocles, that he was able to proceed to the siege of Syracuse. Although this city was strongly fortified, Agathocles had no effective army, and he had decided upon a desperate gamble: in August 310, he had sailed away from Sicily, and had invaded the Carthaginian homeland, Africa (modern Tunisia). Here, he won a brilliant victory, and he proceeded against Carthage itself.
At this stage, he concluded the treaty with Ophellas. The ruler of Cyrenaica was to bring new soldiers, and in return would be made Agathocles' governor at Carthage. To Ophellas, this offered beautiful prospects: being the viceroy of two masters, in territories that were separated from his master's countries by the sea and the desert, he would have almost regal powers. (This was of course unacceptable to Ptolemy.) Ophellas recruited many mercenaries, especially from Athens, and started his march to Carthage in the late summer of 308. Two months later, he arrived in Africa.
Almost immediately, the two commanders started to quarrel, and Ophellas was assassinated in November. It is possible that Agathocles had planned the murder all along, maybe in cooperation with Ptolemy (both men were quite capable of an intrigue like that). However this may be, Ophellas' mercenaries had little choice and sided with Agathocles, who left them behind, returned to Sicily, and concluded a peace treaty with Carthage that left him in control of Sicily east of the Halycus. The mercenaries, left alone, were killed by the Carthaginians.
Ophellas had been married to an Athenian lady named Eurydice, a descendant of Miltiades, the famous general who had defeated the Persians at Marathon (490). She returned to Athens, where she married Demetrius Poliorcetes.