Which well lies at the root of Yggdrasil in Asgard?

Urðarbrunnr is the well beneath Yggdrasil’s root that reaches the realm of the Æsir, commonly identified with Asgard.

The well is central to the work of the three principal Norns: Urðr, Verðandi, and Skuld. In the Poetic Edda, the Norns emerge from or dwell by the well and shape the destinies of gods and humans. In the Prose Edda, the gods also cross Bifröst to hold council near it.

Urðarbrunnr is one of three major wells associated with Yggdrasil’s roots. Hvergelmir lies beneath another root in Niflheim, while Mímisbrunnr is associated with Mímir and the land of the frost giants. These locations are often mixed up because all three are tied to the world tree.

The well’s name means “Urðr’s well” or “well of fate.” Snorri also says that the Norns use its water and surrounding mud to protect Yggdrasil from decay.