The Ptolemaic dynasty (/ˌtɒlɪˈmeɪ.ɪk/; Ancient Greek: Πτολεμαῖοι, Ptolemaioi), also known as the Lagid dynasty (Λαγίδαι, Lagidai; after Ptolemy I's father, Lagus), was a Macedonian Greek royal house which ruled the Ptolemaic Kingdom in Ancient Egypt during the Hellenistic period. Reigning for 275 years, the Ptolemaic was the longest and last dynasty of ancient Egypt from 305 BC until its incorporation into the Roman Republic in 30 BC.
Ptolemy, a general and one of the somatophylakes (bodyguard companions) of Alexander the Great, was appointed satrap of Egypt after Alexander's death in 323 BC. In 305 BC he declared himself Pharaoh Ptolemy I, later known as Sōter "Saviour". The Egyptians soon accepted the Ptolemies as the successors to the pharaohs of independent Egypt. The new dynasty showed respect to local traditions and adopted the Egyptian titles and iconography, while also preserving their own Greek language and culture. The Ptolemaic period was marked by the intense interactions and blending of the Greek and Egyptian cultures. Under the Ptolemies, Hellenistic religion was largely shaped by religious syncretism and imperial cult. Elements of Greek education became widespread in urban spaces, culminating in the foundation of the Mouseion (including the Library of Alexandria) and the Serapeum. During the Hellenistic period, the city of Alexandria, founded by Alexander the Great, would gradually surpass Athens as the intellectual centre of the Mediterranean world.