In Norse mythology, Andvarinaut was a magical ring, first owned by Andvari.

The ring was cursed during its deceitful acquisition from Andvari by Loki. In revenge, Andvari cursed the ring to bring destruction on its owner.

Loki disposed of it by immediately giving it to King Hriedmar of the dwarves (as a "reparation" since Loki and the other Aesir had killed his son, Otr, inadvertently). Hriedmar's son, Fafnir, then killed him and took the ring. Sigurd then killed Fafnir and gave it to Brünnehilde, who killed herself when he left her.

Some scholars have made speculative claims that Andvarinaut is the origin of the curse of the Hope diamond.

The ring is one of the central items in Richard Wagner's Der Ring des Nibelungen (in English, The Ring of the Nibelung) and is considered to have inspired J. R. R. Tolkien's The Lord of the Rings.