- The Sumerians, who were one of the earliest civilizations to develop in Mesopotamia (modern-day Iraq) in the 4th millennium BC. The Sumerians developed a system of writing, known as cuneiform, and built some of the world's first cities, including Ur and Uruk.
- The Akkadians, who were a Semitic people who conquered Sumer in the 23rd century BC and established the Akkadian Empire. The Akkadians adopted many of the Sumerian cultural and technological achievements, and they spread their culture and language throughout Mesopotamia.
- The Babylonians, who were another Semitic people who succeeded the Akkadians and established the Babylonian Empire in the 18th century BC. The Babylonians built some of the most famous ancient structures, including the Hanging Gardens of Babylon and the Ishtar Gate.
- The Assyrians, who were a Semitic people who established the Assyrian Empire in the 10th century BC. The Assyrians were known for their military prowess and they conquered a vast territory that stretched from the Persian Gulf to the Mediterranean Sea.
- The Persians, who conquered the Assyrian Empire in the 6th century BC and established the Persian Empire. The Persians ruled over Iraq for several centuries and they introduced many new cultural and administrative practices.
- The Arabs, who conquered Iraq in the 7th century AD and introduced Islam. The Arabs ruled over Iraq for over a thousand years and they made Iraq a center of Islamic learning and culture.
- The Mongols, who invaded Iraq in the 13th century AD and destroyed many of its cities, including Baghdad. The Mongols were eventually driven out of Iraq by the Mamluks, an Egyptian military dynasty.
- The Ottomans, who conquered Iraq in the 16th century AD and ruled over the country for over four centuries. The Ottomans were defeated in World War I and Iraq was placed under British control.
- The British, who ruled over Iraq from 1920 to 1932. The British established a monarchy in Iraq and they helped to develop the country's infrastructure and economy.
- The Hashemites, who ruled over Iraq from 1932 to 1958. The Hashemites were overthrown in a military coup in 1958.
- The Baathists, who ruled over Iraq from 1968 to 2003. The Baathists were a socialist party and they implemented a number of social and economic reforms. The Baathists were also involved in a number of wars, including the Iran-Iraq War and the Gulf War.
- The United States and its allies, who invaded Iraq in 2003 and overthrew the Baathist regime. The United States has been involved in Iraq ever since and it has helped to establish a new democratic government.