Seyyed Ali Hosseini Khamenei is an Iranian Twelver Shia marja' and politician who has been the second supreme leader of Iran since 1989. He previously served as third president of Iran from 1981 to 1989. Khamenei is the longest-serving head of state in the Middle East, as well as the second-longest-serving Iranian leader of the last century, after Shah Mohammad Reza Pahlavi.

Twelver Shīʿism, also known as Imāmiyya, is the largest branch of Shīʿa Islam, comprising about 85 percent of all Shīʿa Muslims. The term Twelver refers to its adherents' belief in twelve divinely ordained leaders, known as the Twelve Imams, and their belief that the last Imam, Imam al-Mahdi, lives in Occultation and will reappear as the promised Mahdi.