A ziggurat (/ˈzɪɡʊˌræt/; Cuneiform: 𒅆𒂍𒉪, Akkadian: ziqqurratum, D-stem of zaqārum 'to protrude, to build high', cognate with other Semitic languages like Hebrew zaqar (זָקַר) 'protrude') is a type of massive structure built in ancient Mesopotamia and Iran. It has the form of a terraced compound of successively receding stories or levels. Notable ziggurats include the Great Ziggurat of Ur near Nasiriyah, the Ziggurat of Aqar Quf near Baghdad, the no longer extant Etemenanki in Babylon, Chogha Zanbil in Khūzestān and Sialk. The Sumerians believed that the gods lived in the temple at the top of the ziggurats, so only priests and other highly-respected individuals could enter. Sumerian society offered these individuals such gifts as music, harvested produce, and the creation of devotional statues to entice them to live in the temple.

The word ziggurat comes from ziqqurratum (height, pinnacle), in ancient Assyrian. From zaqārum, to be high up. The Ziggurat of Ur is a Neo-Sumerian ziggurat built by King Ur-Nammu, who dedicated it in honor of Nanna/Sîn in approximately the 21st century BC during the Third Dynasty of Ur. These are only a few but are not all of them as there are so many ziggurats in the world built by ancient civilizations.

Ziggurats were built by ancient Sumerians, Akkadians, Elamites, Eblaites and Babylonians for local religions. Each ziggurat was part of a temple complex with other buildings. Before the ziggurats there were raised platforms that date from the Ubaid period during the sixth millennium BCE. The ziggurats began as platforms (usually oval, rectangular or square). The ziggurat was a mastaba-like structure with a flat top. The sun-baked bricks made up the core of the ziggurat with facings of fired bricks on the outside. Each step was slightly smaller than the step below it. The facings were often glazed in different colors and may have had astrological significance. Kings sometimes had their names engraved on these glazed bricks. The number of floors ranged from two to seven.

According to archaeologist Harriet Crawford,

It is usually assumed that the ziggurats supported a shrine, though the only evidence for this comes from Herodotus, and physical evidence is non-existent ... The likelihood of such a shrine ever being found is remote. Erosion has usually reduced the surviving ziggurats to a fraction of their original height, but textual evidence may yet provide more facts about the purpose of these shrines. In the present state of our knowledge it seems reasonable to adopt as a working hypothesis the suggestion that the ziggurats developed out of the earlier temples on platforms and that small shrines stood on the highest stages ...

Access to the shrine would have been by a series of ramps on one side of the ziggurat or by a spiral ramp from base to summit. The Mesopotamian ziggurats were not places for public worship or ceremonies. They were believed to be dwelling places for the gods, and each city had its own patron god. Only priests were permitted on the ziggurat or in the rooms at its base, and it was their responsibility to care for the gods and attend to their needs. The priests were very powerful members of Sumerian and Assyro-Babylonian society.

One of the best-preserved ziggurats is Chogha Zanbil in western Iran. The Sialk ziggurat, in Kashan, Iran, is the oldest known ziggurat, dating to the early 3rd millennium BCE. Ziggurat designs ranged from simple bases upon which a temple sat, to marvels of mathematics and construction which spanned several terraced stories and were topped with a temple.

An example of a simple ziggurat is the White Temple of Uruk, in ancient Sumer. The ziggurat itself is the base on which the White Temple is set. Its purpose is to get the temple closer to the heavens,^{[citation needed]} and provide access from the ground to it via steps. The Mesopotamians believed that these pyramid temples connected heaven and earth. In fact, the ziggurat at Babylon was known as Etemenanki, which means "House of the foundation of heaven and earth" in Sumerian.