Who was ozymandias?

"Ozymandias"

The first-person poetic persona states that he met a traveler who had been to “an antique land.” The traveler told him that he had seen a vast but ruined statue, where only the legs remained standing. The face was sunk in the sand, frowning and sneering. The sculptor interpreted his subject well. There also was a pedestal at the statue, where the traveler read that the statue was of “Ozymandias, King of Kings.” Although the pedestal told “mighty” onlookers that they should look out at the King’s works and thus despair at his greatness, the whole area was just covered with flat sand. All that is left is the wrecked statue.