Who was the leader of Iraq?

Iraq has a large number of rulers in its history, even if we constrain our view to the "independent Iraq" period. In the Kingdom of Iraq period, Iraq was a constitutional monarchy with a very powerful monarch. In the Iraqi Republic period, Iraq was a Presidential Republic, where the President was the supreme authority. In the Republic of Iraq Period, Iraq has become a Parliamentary Republic where the Prime Minister is the supreme authority and the President is a more ceremonial position.

Kingdom of Iraq: 1923-1958 (Kings of the Hashemite Dynasty)

• Faisal I - 1921-1933
• Ghazi I - 1933-1939
• Faisal II - 1939-1958
  

Iraqi Republic: 1958-2003 (Presidents)

• Muhammad Najib ar-Ruba'i (with Abd el-Karim Qasim) - 1958-1963
• Abdul Salam Arif - 1963-1966
• Abdul Rahman Arif - 1966-1968
• Ahmed Hassan al-Bakr - 1968-1979
• Saddam Hussein - 1979-2003
  

Coalition Occupation 2003-2004

Republic of Iraq: 2004-Present (Prime Ministers)

• Ayad Allawi - 2004-2005
• Ibrahm al-Jaafari - 2005-2006
• Nouri al-Maliki - 2006-2014
• Haider al-Abadi - 2014-Present