Considering that Antigonus was the most powerful another four diadochi combined their forces. Antigonus was defeated along with the former Empire of Alexander the Great was split among his generals to five countries. Egypt handed to Ptolemy I Soter who proclaimed himself King of Egypt at 305 BC and established that the 31st dynasty commonly called Ptolemaic Dynasty which ruled Egypt until the Roman conquest in 30 BC.
Ptolemaic Egypt attained its height under the principle of their very first Ptolemaic pharaohs – Ptolemy I, Ptolemy II and Ptolemy III. Ptolemaic rulers didn’t alter the political system the early Egyptian civilization. The standard religious beliefs lasted, and the Egyptians approved the Ptolemaic rulers of Egypt as equal pharaohs and celestial beings. Ptolemaic pharaohs also kept strictly hierarchical, centralized and bureaucratic system that was current in all sections of life: government, government, military, authority as well as financing and economy.
Ptolemy III was following his departure at 221 BC succeeded by his son Ptolemy IV who had been not able to continue successful coverage of his predecessors though he was able to repulse the assault of Seleucid ruler Antiochus III the Great in the Battle of Raphia in 217 BC. Nevertheless, a series of rebellions broke out soon after the victory in Raphia that was especially serious in southern Egypt and significantly weakened the economic strength of Egypt in addition to the energy of Ptolemaic pharaohs. The decline of Ptolemaic power became evident after the death of Ptolemy IV at 204 BC. His son and successor Ptolemy V was in the time of his departure small, Antiochus III and Philip V of Macedon concluded a secret treaty to grab Egypt. Helpless against allied Seleucid and Macedon compels Egypt has been made to reach an alliance with the Rome which finally led to Roman hindrance into Egyptian affairs.
The final and the most well-known Ptolemaic pharaoh was Cleopatra VII who ruled Egypt from 51 BC until her departure. Cleopatra attempted to reestablish the power of Egypt and to find loose of Roman sway first through Julius Caesar and after his assassination in 44BC during Mark Anthony. But, her influence significantly outperforming the Romans and Octavian (later Emperor Augustus) announced a war against Cleopatra and Mark Anthony. Joined forces of Mark Anthony and Cleopatra were defeated by Octavian at the naval Battle of Actium in 31 BC, while Mark Anthony and Cleopatra retreated to Alexandria to shield themselves out of Egypt. But they neglected against the Roman army headed by Octavian and Mark Anthony, and Cleopatra committed suicide. Together with Cleopatra’s death in 30 BC that the Ptolemaic Dynasty became extinct. Her son out of connection with Julius Caesar – Caesarion, afterwards Ptolemy XIV was assassinated on Octavian’s arrangement, although Egypt became a Roman province.