Ayatollah Ali Khamenei is the supreme leader of Iran. The nature of his job highlights the "Islamic" part of the "Islamic Republic of Iran" and plays down the "republic" part. He pretty much has the power to overrule any acts of the Iranian legislature and president. He's also an unelected theocrat who seems to be really interested in nukes.
He was born in Mashhad on the 17th of July 1939.
Not to be confused with Ayatollah Ruhollah Khomeini, who was supreme leader during the Iran hostage crisis.