Norse cosmology is the account of the universe and its laws by the ancient North Germanic peoples. The topic encompasses concepts from Norse mythology and Old Norse religion such as notations of time and space, cosmogony, personifications, anthropogeny, and eschatology. Like other aspects of Norse mythology, these concepts are primarily recorded from earlier oral sources in the Poetic Edda, a collection of poems compiled in the 13th century, and the Prose Edda, attributed to the Icelander Snorri Sturluson in the 13th century. Together these sources depict an image of Nine Worlds around a cosmic tree, Yggdrasil.

Concepts of time and space play a major role in the Old Norse corpus's presentation of Norse cosmology. While events in Norse mythology describe a somewhat linear progression, various scholars in ancient Germanic studies note that Old Norse texts may imply or directly describe a fundamental belief in cyclic time. According to scholar John Lindow, "the cosmos might be formed and reformed on multiple occasions by the rising sea."

Drawing in part on various eddic poems, the Gylfaginning section of the Prose Edda contains an account of the development and creation of the cosmos: long before the Earth came to be, there existed the bright and flaming place called Muspell—a location so hot that foreigners may not enter it—and the foggy land of Niflheim. In Niflheim was a spring, Hvergelmir, and from it flow numerous rivers. Together these rivers, known as Élivágar, flowed further and further from their source. Eventually the poisonous substance within the flow came to harden and turn to ice. When the flow became entirely solid, a poisonous vapor rose from the ice and solidified into rime atop the solid river. These thick ice layers grew, in time spreading across the void of Ginnungagap.

The northern region of Ginnungagap continued to fill with weight from the growing substance and its accompanying blowing vapor, yet the southern portion of Ginnungagap remained clear due to its proximity to the sparks and flames of Muspell. Between Niflheim and Muspell, ice and fire, was a placid location, "as mild as a windless sky". When the rime and the blowing heat met, the liquid melted and dropped, and this mixture formed the primordial being Ymir, the ancestor of all jötnar. Ymir sweated while sleeping. From his left arm grew a male and female jötunn, "and one of his legs begot a son with another", and these limbs too produced children.

Ymir fed from rivers of milk that flowed from the teats of the primordial cow, Auðumbla. Auðumbla fed from salt she licked from rime stones. Over the course of three days, she licked free a beautiful and strong man, Búri. Búri's son Borr married a jötunn named Bestla, and the two had three sons: the gods Odin, Vili and Vé. The sons killed Ymir, and Ymir's blood poured across the land, producing great floods that killed all of the jötnar but two (Bergelmir and his unnamed wife, who sailed across the flooded landscape).

Odin, Vili, and Vé took Ymir's corpse to the center of Ginnungagap and carved it. They made the earth from Ymir's flesh; the rocks from his bones; from his blood the sea, lakes, and oceans; and scree and stone from his molars, teeth, and remaining bone fragments. They surrounded the earth's lands with sea, forming a circle. From Ymir's skull they made the sky, which they placed above the earth in four points, each held by a dwarf (Norðri, Suðri, Austri and Vestri—Old Norse 'north, south, east, and west', respectively).

After forming the dome of the Earth, the brothers Odin, Vili and Vé took sparks of light from Muspell and placed them around the Earth, both above and below. Some remained fixed and others moved through the sky in predetermined courses. The trio provided land for the jötnar to leave by the sea. Using Ymir's eyelashes, the trio built a fortification around the center of the landmass to contain the hostility of the jötnar. They called this fortification Miðgarðr (Old Norse 'central enclosure'). Finally, from Ymir's brains, they formed the clouds.

From Ymir's eyebrows they crafted a stronghold named Midgard. When they were walking along the seashore, they found two trees and shaped humans of them. Odin gave them spirit and life, Vili gave them wit and feeling, and Vé gave them form, speech, hearing, and sight. They gave them clothing and names: the man was called Askr, and the woman Embla. They were the ancestors of mankind who lived in Midgard. The brothers made for themselves in the middle of the world a city called Asgard, where the gods lived.