Iraq, a country located in West Asia, largely coincides with the ancient region of Mesopotamia, often referred to as the cradle of civilization. The history of Mesopotamia extends back to the Lower Paleolithic period, with significant developments continuing through the establishment of the Caliphate in the late 7th century AD, after which the region became known as Iraq. Within its borders lies the ancient land of Sumer, which emerged between 6000 and 5000 BC during the Neolithic Ubaid period. Sumer is recognized as the world's earliest civilization, marking the beginning of urban development, written language, and monumental architecture. Iraq's territory also includes the heartlands of the Akkadian, Neo-Sumerian, Babylonian, Neo-Assyrian, and Neo-Babylonian empires, which dominated Mesopotamia and much of the Ancient Near East during the Bronze and Iron Ages.

Iraq was a center of innovation in antiquity, producing early written languages, literary works, and significant advancements in astronomy, mathematics, law, and philosophy. This era of indigenous rule ended in 539 BC when the Neo-Babylonian Empire was conquered by the Achaemenid Empire under Cyrus the Great, who declared himself the "King of Babylon." The city of Babylon, the ancient seat of Babylonian power, became one of the key capitals of the Achaemenid Empire.

In the following centuries, the regions constituting modern Iraq came under the control of several empires, including the Greeks, Parthians, and Romans, establishing new centers like Seleucia and Ctesiphon. By the 3rd century AD, the region fell under Persian control through the Sasanian Empire, during which time Arab tribes from South Arabia migrated into Lower Mesopotamia, leading to the formation of the Sassanid-aligned Lakhmid kingdom. The Arabic name al-ʿIrāq likely originated during this period. The Sasanian Empire was eventually conquered by the Rashidun Caliphate in the 7th century, bringing Iraq under Islamic rule after the Battle of al-Qadisiyyah in 636. The city of Kufa, founded shortly thereafter, became a central hub for the Rashidun dynasty until their overthrow by the Umayyads in 661.

With the rise of the Abbasid Caliphate in the mid-8th century, Iraq became the center of Islamic rule, with Baghdad, founded in 762, serving as the capital. Baghdad flourished during the Islamic Golden Age, becoming a global center for culture, science, and intellectualism. However, the city's prosperity declined following the Buwayhid and Seljuq invasions in the 10th century and suffered further with the Mongol invasion of 1258. Iraq came under Ottoman rule in the 16th century and, apart from a Safavid occupation from 1623 to 1638, remained part of the empire until the end of World War I, after which Mandatory Iraq was established by the British Empire. Initially united under the province of Baghdad, Ottoman Iraq was by the 17th century divided into the provinces of Baghdad, Basra, Mosul, and Shahrizor, which Ottoman officials collectively referred to as Hıtta-i Irakiyye ("the Iraq Region"). Iraq gained independence in 1932 as the Kingdom of Iraq, which became a republic in 1958. The modern era has seen Iraq facing challenges, including the rule of Saddam Hussein, the 2003 invasion of Iraq, and subsequent efforts to rebuild the country amidst sectarian violence and the rise of the Islamic State. Despite these difficulties, Iraq plays a vital role in the geopolitics of the Middle East.

Between 65,000 BC and 35,000 BC, northern Iraq was home to a Neanderthal culture, archaeological remains of which have been discovered at Shanidar Cave. During 1957–1961, Shanidar Cave was excavated by Ralph Solecki and his team from Columbia University, uncovering nine skeletons of Neanderthal man of varying ages and states of preservation (labelled Shanidar I–IX). A tenth individual was later discovered by M. Zeder during examination of a faunal assemblage from the site at the Smithsonian Institution. The remains seemed to suggest that Neanderthals had funeral ceremonies, burying their dead with flowers (although the flowers are now thought to be a modern contaminant), and that they took care of injured and elderly individuals.

This region is also the location of a number of pre-Neolithic burials, dating from approximately 11,000 BC. Since approximately 10,000 BC, Iraq, together with a large part of the Fertile Crescent, was a center of a Neolithic culture known as Pre-Pottery Neolithic A (PPNA), where agriculture and cattle breeding appeared for the first time. In Iraq, this period has been excavated at sites like M'lefaat and Nemrik 9. The following Neolithic period, PPNB, is represented by rectangular houses. At the time of the pre-pottery Neolithic, people used vessels made of stone, gypsum, and burnt lime (Vaisselle blanche). Finds of obsidian tools from Anatolia are evidence of early trade relations. Further important sites of human advancement were Jarmo (circa 7100 BC), a number of sites belonging to the Halaf culture, and Tell al-'Ubaid, the type site of the Ubaid period (between 6500 BC and 3800 BC).

Mesopotamia is the site of the earliest developments of the Neolithic Revolution from around 10,000 BC. It has been identified as having "inspired some of the most important developments in human history including the invention of the wheel, the planting of the first cereal crops, and the development of cursive script, mathematics, astronomy, and agriculture."

The "Cradle of Civilisation" is a common term for the area comprising modern Iraq as it was home to the earliest known civilisation, the Sumerian civilisation, which arose in the fertile Tigris-Euphrates river valley of southern Iraq in the Chalcolithic (Ubaid period). It was there, in the late 4th millennium BC, that the world's first known writing system emerged. The Sumerians were also the first known to harness the wheel and create city-states; their writings record the first known evidence of mathematics, astronomy, astrology, written law, medicine, and organised religion. The Sumerian language is a language isolate. The major city-states of the early Sumerian period included Eridu, Bad-tibira, Larsa, Sippar, Shuruppak, Uruk, Kish, Ur, Nippur, Lagash, Girsu, Umma, Hamazi, Adab, Mari, Isin, Kutha, Der, and Akshak. The cities to the north, like Ashur, Arbela (modern Erbil), and Arrapha (modern Kirkuk), were also extant in what was to be called Assyria from the 25th century BC; however, at this stage, they were Sumerian-ruled administrative centers.