What is the name of the well of wisdom guarded by Mimir?

The well of wisdom guarded by Mimir is called Mímisbrunnr in Norse mythology.

Mímisbrunnr lies beneath one of the three roots of Yggdrasil, the immense world tree at the center of Norse cosmology. Its waters contain wisdom and understanding, and Mimir, renowned for his knowledge, drinks from it. The name means “Mimir’s wellspring” or “Mimir’s well.”

The Prose Edda tells that Odin sought a drink from the well but had to leave one of his eyes as a pledge. This sacrifice explains why Odin is often portrayed as a god who willingly gives up part of himself in pursuit of knowledge. The Poetic Edda also connects Mimir and the well with hidden wisdom, though some details are obscure and vary by interpretation.

Mímisbrunnr is not the same as Urðarbrunnr, associated with the Norns, or Hvergelmir, a spring linked with Niflheim and primordial rivers. Gjöll is also different: it is principally known as a river or boundary in the underworld, not Mimir’s wisdom well.