For the astronomer, see Ptolemy; for others named "Ptolemy" or "Ptolemaeus", see Ptolemy (disambiguation).

Ptolemy I Soter I (, Ptolemaĩos Sōtḗr, i.e. Ptolemy (pronounced ) the Savior), also known as Ptolemy Lagides, c. 367 BC – c. 283 BC, was a Macedonian general under Alexander the Great, who became ruler of Egypt (323–283 BC) and founder of the Ptolemaic Kingdom and dynasty. In 305/4 BC he demanded the title of pharaoh. His successors ruled Egypt for approximately three centuries, turning Egypt into a Hellenistic kingdom and a center of Greek culture.